CINXE.COM

<!DOCTYPE html> <html lang="en" dir="ltr" class="client-nojs"> <head><script type="text/javascript" src="/_static/js/bundle-playback.js?v=HxkREWBo" charset="utf-8"></script> <script type="text/javascript" src="/_static/js/wombat.js?v=txqj7nKC" charset="utf-8"></script> <script>window.RufflePlayer=window.RufflePlayer||{};window.RufflePlayer.config={"autoplay":"on","unmuteOverlay":"hidden"};</script> <script type="text/javascript" src="/_static/js/ruffle/ruffle.js"></script> <script type="text/javascript"> __wm.init("https://web.archive.org/web"); __wm.wombat("https://en.wikipedia.org/wiki/Clock","20150320193459","https://web.archive.org/","web","/_static/", "1426880099"); </script> <link rel="stylesheet" type="text/css" href="/_static/css/banner-styles.css?v=S1zqJCYt" /> <link rel="stylesheet" type="text/css" href="/_static/css/iconochive.css?v=3PDvdIFv" />  <meta charset="UTF-8"/> <title>Clock - Wikipedia, the free encyclopedia</title> <meta name="generator" content="MediaWiki 1.25wmf21"/> <link rel="alternate" href="https://web.archive.org/web/20150320193459/android-app://org.wikipedia/http/en.m.wikipedia.org/wiki/Clock"/> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit"/> <link rel="edit" title="Edit this page" href="/w/index.php?title=Clock&action=edit"/> <link rel="apple-touch-icon" href="//web.archive.org/web/20150320193459im_/https://bits.wikimedia.org/apple-touch/wikipedia.png"/> <link rel="shortcut icon" href="//web.archive.org/web/20150320193459im_/https://bits.wikimedia.org/favicon/wikipedia.ico"/> <link rel="search" type="application/opensearchdescription+xml" href="/web/20150320193459/https://en.wikipedia.org/w/opensearch_desc.php" title="Wikipedia (en)"/> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"/> <link rel="alternate" hreflang="x-default" href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock"/> <link rel="copyright" href="//web.archive.org/web/20150320193459/https://creativecommons.org/licenses/by-sa/3.0/"/> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Special:RecentChanges&feed=atom"/> <link rel="canonical" href="https://web.archive.org/web/20150320193459/http://en.wikipedia.org/wiki/Clock"/> <link rel="stylesheet" href="//web.archive.org/web/20150320193459cs_/https://bits.wikimedia.org/en.wikipedia.org/load.php?debug=false&lang=en&modules=ext.gadget.DRN-wizard%2CReferenceTooltips%2Ccharinsert%2Cfeatured-articles-links%2CrefToolbar%2Cswitcher%2Cteahouse%7Cext.rtlcite%2Cwikihiero%2CwikimediaBadges%7Cext.uls.nojs%7Cext.visualEditor.viewPageTarget.noscript%7Cmediawiki.legacy.commonPrint%2Cshared%7Cmediawiki.sectionAnchor%7Cmediawiki.skinning.interface%7Cmediawiki.ui.button%7Cmw.PopUpMediaTransform%7Cskins.vector.styles%7Cwikibase.client.init&only=styles&skin=vector&*"/> <meta name="ResourceLoaderDynamicStyles" content=""/> <link rel="stylesheet" href="//web.archive.org/web/20150320193459cs_/https://bits.wikimedia.org/en.wikipedia.org/load.php?debug=false&lang=en&modules=site&only=styles&skin=vector&*"/> <style>a:lang(ar),a:lang(kk-arab),a:lang(mzn),a:lang(ps),a:lang(ur){text-decoration:none} /* cache key: enwiki:resourceloader:filter:minify-css:7:3904d24a08aa08f6a68dc338f9be277e */</style> <script src="//web.archive.org/web/20150320193459js_/https://bits.wikimedia.org/en.wikipedia.org/load.php?debug=false&lang=en&modules=startup&only=scripts&skin=vector&*"></script> <script>if(window.mw){ mw.config.set({"wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"Clock","wgTitle":"Clock","wgCurRevisionId":652709305,"wgRevisionId":652709305,"wgArticleId":6449,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["Use mdy dates from November 2013","All articles with unsourced statements","Articles with unsourced statements from November 2014","Articles with unsourced statements from May 2010","Wikipedia articles needing page number citations from July 2011","Articles with unsourced statements from October 2007","Wikipedia articles needing clarification from November 2014","Commons category with local link same as on Wikidata","Clocks"],"wgBreakFrames":false,"wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy","wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgMonthNamesShort":["","Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"],"wgRelevantPageName":"Clock","wgRelevantArticleId":6449,"wgIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":["sysop"],"wgWikiEditorEnabledModules":{"toolbar":true,"dialogs":true,"hidesig":true,"preview":false,"publish":false},"wgBetaFeaturesFeatures":[],"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr"},"wikilove-recipient":"","wikilove-anon":0,"wgPoweredByHHVM":true,"wgULSAcceptLanguageList":[],"wgULSCurrentAutonym":"English","wgFlaggedRevsParams":{"tags":{"status":{"levels":1,"quality":2,"pristine":3}}},"wgStableRevisionId":null,"wgCategoryTreePageCategoryOptions":"{\"mode\":0,\"hideprefix\":20,\"showcount\":true,\"namespaces\":false}","wgNoticeProject":"wikipedia","wgWikibaseItemId":"Q376"}); }</script><script>if(window.mw){ mw.loader.implement("user.options",function($,jQuery){mw.user.options.set({"variant":"en"});},{},{},{});mw.loader.implement("user.tokens",function($,jQuery){mw.user.tokens.set({"editToken":"+\\","patrolToken":"+\\","watchToken":"+\\"});},{},{},{}); /* cache key: enwiki:resourceloader:filter:minify-js:7:94007ea073e20ad4a3cdce36b2f2e369 */ }</script> <script>if(window.mw){ mw.loader.load(["mw.TMHGalleryHook.js","mediawiki.page.startup","mediawiki.legacy.wikibits","mediawiki.legacy.ajax","ext.centralauth.centralautologin","mmv.head","ext.imageMetrics.head","ext.visualEditor.viewPageTarget.init","ext.uls.init","ext.uls.interface","ext.centralNotice.bannerController","skins.vector.js"]); }</script> <link rel="dns-prefetch" href="//web.archive.org/web/20150320193459/https://meta.wikimedia.org/"/>  </head> <body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-Clock skin-vector action-view"> <div id="mw-page-base" class="noprint"></div> <div id="mw-head-base" class="noprint"></div> <div id="content" class="mw-body" role="main"> <a id="top"></a> <div id="siteNotice"></div> <div class="mw-indicators"> </div> <h1 id="firstHeading" class="firstHeading" lang="en">Clock</h1> <div id="bodyContent" class="mw-body-content"> <div id="siteSub">From Wikipedia, the free encyclopedia</div> <div id="contentSub"></div> <div id="jump-to-nav" class="mw-jump"> Jump to: <a href="#mw-head">navigation</a>, <a href="#p-search">search</a> </div> <div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><div class="hatnote">For other uses, see <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_(disambiguation)" title="Clock (disambiguation)" class="mw-disambig">Clock (disambiguation)</a>.</div> <div class="hatnote">"Timepiece" redirects here. For the Kenny Rogers album, see <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Timepiece_(album)" title="Timepiece (album)">Timepiece (album)</a>.</div> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:BahnhofsuhrZuerich_RZ.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/BahnhofsuhrZuerich_RZ.jpg/220px-BahnhofsuhrZuerich_RZ.jpg" width="220" height="220" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/BahnhofsuhrZuerich_RZ.jpg/330px-BahnhofsuhrZuerich_RZ.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/b/b7/BahnhofsuhrZuerich_RZ.jpg/440px-BahnhofsuhrZuerich_RZ.jpg 2x" data-file-width="1100" data-file-height="1100"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:BahnhofsuhrZuerich_RZ.jpg" class="internal" title="Enlarge"></a></div> The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Swiss_railway_clock" title="Swiss railway clock">Swiss railway clock</a>.</div> </div> </div> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Greenwich_clock.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Greenwich_clock.jpg/220px-Greenwich_clock.jpg" width="220" height="410" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Greenwich_clock.jpg/330px-Greenwich_clock.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/1/1b/Greenwich_clock.jpg/440px-Greenwich_clock.jpg 2x" data-file-width="1368" data-file-height="2549"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Greenwich_clock.jpg" class="internal" title="Enlarge"></a></div> The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Shepherd_gate_clock" title="Shepherd gate clock" class="mw-redirect">Shepherd gate clock</a> at the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Royal_Observatory,_Greenwich" title="Royal Observatory, Greenwich">Royal Observatory, Greenwich</a></div> </div> </div> <p>A <b>clock</b> is an instrument to indicate, keep, and co-ordinate <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time" title="Time">time</a>. The word <i>clock</i> is derived ultimately (via <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Dutch_language" title="Dutch language">Dutch</a>, Northern French, and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Medieval_Latin" title="Medieval Latin">Medieval Latin</a>) from the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Celtic_languages" title="Celtic languages">Celtic</a> words <i>clagan</i> and <i>clocca</i> meaning "<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Bell_(instrument)" title="Bell (instrument)">bell</a>". A silent instrument missing such a mechanism has traditionally been known as a <b>timepiece</b>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span>[</span>1<span>]</span></a></sup> In general usage today a "clock" refers to any device for measuring and displaying the time. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Watch" title="Watch">Watches</a> and other timepieces that can be carried on one's person are often distinguished from clocks.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span>[</span>2<span>]</span></a></sup></p> <p>The clock is one of the oldest human <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Invention" title="Invention">inventions</a>, meeting the need to consistently measure intervals of time shorter than the natural units: the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Day" title="Day">day</a>, the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lunar_month" title="Lunar month">lunar month</a>, and the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Year" title="Year">year</a>. Devices operating on several physical processes have been used over the millennia. A <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sundial" title="Sundial">sundial</a> shows the time by displaying the position of a shadow on a flat surface. There are a range of duration timers, a well-known example being the hourglass. Water clocks, along with the sundials, are possibly the oldest time-measuring instruments. A major advance occurred in Europe around 1300 with the invention of the <i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Escapement" title="Escapement">escapement</a></i>, which allowed construction of the first mechanical clocks, which used oscillating timekeepers like <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Balance_wheel" title="Balance wheel">balance wheels</a>.<sup id="cite_ref-Dohrn_3-0" class="reference"><a href="#cite_note-Dohrn-3"><span>[</span>3<span>]</span></a></sup><sup id="cite_ref-Marrison_4-0" class="reference"><a href="#cite_note-Marrison-4"><span>[</span>4<span>]</span></a></sup><sup id="cite_ref-Cipolla_5-0" class="reference"><a href="#cite_note-Cipolla-5"><span>[</span>5<span>]</span></a></sup><sup id="cite_ref-White_6-0" class="reference"><a href="#cite_note-White-6"><span>[</span>6<span>]</span></a></sup> Spring-driven clocks appeared during the 15th century. During the 15th and 16th centuries, clockmaking flourished. The next development in accuracy occurred after 1656 with the invention of the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pendulum_clock" title="Pendulum clock">pendulum clock</a>. A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electric_clock" title="Electric clock">electric clock</a> was patented in 1840. The development of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electronics" title="Electronics">electronics</a> in the 20th century led to clocks with no clockwork parts at all.</p> <p>The timekeeping element in every modern clock is a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Harmonic_oscillator" title="Harmonic oscillator">harmonic oscillator</a>, a physical object (<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Resonator" title="Resonator">resonator</a>) that vibrates or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Oscillate" title="Oscillate" class="mw-redirect">oscillates</a> repetitively at a precisely constant <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Frequency" title="Frequency">frequency</a>.<sup id="cite_ref-Marrison_4-1" class="reference"><a href="#cite_note-Marrison-4"><span>[</span>4<span>]</span></a></sup> This object can be a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pendulum" title="Pendulum">pendulum</a>, a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tuning_fork" title="Tuning fork">tuning fork</a>, a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Crystal_oscillator" title="Crystal oscillator">quartz crystal</a>, or the vibration of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electron" title="Electron">electrons</a> in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atom" title="Atom">atoms</a> as they emit <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Microwave" title="Microwave">microwaves</a>. Analog clocks usually indicate time using angles. Digital clocks display a numeric representation of time. Two numeric display formats are commonly used on <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_data" title="Digital data">digital</a> clocks: 24-hour notation and 12-hour notation. Most digital clocks use electronic mechanisms and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/LCD" title="LCD" class="mw-redirect">LCD</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/LED" title="LED" class="mw-redirect">LED</a>, or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Vacuum_fluorescent_display" title="Vacuum fluorescent display">VFD</a> displays. For convenience, distance, telephony or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Blindness" title="Blindness">blindness</a>, auditory clocks present the time as sounds. There are also clocks for the blind that have displays that can be read by using the sense of touch. Some of these are similar to normal analog displays, but are constructed so the hands can be felt without damaging them. The evolution of the technology of clocks continues today.</p> <p>The study of timekeeping is known as <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Horology" title="Horology">horology</a>.</p> <p></p> <div id="toc" class="toc"> <div id="toctitle"> <h2>Contents</h2> </div> <ul> <li class="toclevel-1 tocsection-1"><a href="#History"><span class="tocnumber">1</span> <span class="toctext">History</span></a></li> <li class="toclevel-1 tocsection-2"><a href="#Time-measuring_devices"><span class="tocnumber">2</span> <span class="toctext">Time-measuring devices</span></a> <ul> <li class="toclevel-2 tocsection-3"><a href="#Sundials"><span class="tocnumber">2.1</span> <span class="toctext">Sundials</span></a></li> <li class="toclevel-2 tocsection-4"><a href="#Devices_that_measure_duration.2C_elapsed_time_and.2For_intervals"><span class="tocnumber">2.2</span> <span class="toctext">Devices that measure duration, elapsed time and/or intervals</span></a></li> <li class="toclevel-2 tocsection-5"><a href="#Water_clocks"><span class="tocnumber">2.3</span> <span class="toctext">Water clocks</span></a></li> <li class="toclevel-2 tocsection-6"><a href="#Early_mechanical_clocks"><span class="tocnumber">2.4</span> <span class="toctext">Early mechanical clocks</span></a></li> <li class="toclevel-2 tocsection-7"><a href="#Astronomical_clocks"><span class="tocnumber">2.5</span> <span class="toctext">Astronomical clocks</span></a></li> <li class="toclevel-2 tocsection-8"><a href="#Spring-driven_clocks"><span class="tocnumber">2.6</span> <span class="toctext">Spring-driven clocks</span></a></li> <li class="toclevel-2 tocsection-9"><a href="#Pendulum_clock"><span class="tocnumber">2.7</span> <span class="toctext">Pendulum clock</span></a></li> <li class="toclevel-2 tocsection-10"><a href="#Hairspring"><span class="tocnumber">2.8</span> <span class="toctext">Hairspring</span></a></li> <li class="toclevel-2 tocsection-11"><a href="#Marine_chronometer"><span class="tocnumber">2.9</span> <span class="toctext">Marine chronometer</span></a></li> <li class="toclevel-2 tocsection-12"><a href="#Mass_production"><span class="tocnumber">2.10</span> <span class="toctext">Mass production</span></a></li> <li class="toclevel-2 tocsection-13"><a href="#Electric_clocks"><span class="tocnumber">2.11</span> <span class="toctext">Electric clocks</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-14"><a href="#How_clocks_work"><span class="tocnumber">3</span> <span class="toctext">How clocks work</span></a> <ul> <li class="toclevel-2 tocsection-15"><a href="#Power_source"><span class="tocnumber">3.1</span> <span class="toctext">Power source</span></a></li> <li class="toclevel-2 tocsection-16"><a href="#Oscillator"><span class="tocnumber">3.2</span> <span class="toctext">Oscillator</span></a> <ul> <li class="toclevel-3 tocsection-17"><a href="#Synchronized_or_slave_clocks"><span class="tocnumber">3.2.1</span> <span class="toctext">Synchronized or slave clocks</span></a></li> </ul> </li> <li class="toclevel-2 tocsection-18"><a href="#Controller"><span class="tocnumber">3.3</span> <span class="toctext">Controller</span></a></li> <li class="toclevel-2 tocsection-19"><a href="#Counter_chain"><span class="tocnumber">3.4</span> <span class="toctext">Counter chain</span></a></li> <li class="toclevel-2 tocsection-20"><a href="#Indicator"><span class="tocnumber">3.5</span> <span class="toctext">Indicator</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-21"><a href="#Types"><span class="tocnumber">4</span> <span class="toctext">Types</span></a> <ul> <li class="toclevel-2 tocsection-22"><a href="#Time_display_methods"><span class="tocnumber">4.1</span> <span class="toctext">Time display methods</span></a> <ul> <li class="toclevel-3 tocsection-23"><a href="#Analog_clocks"><span class="tocnumber">4.1.1</span> <span class="toctext">Analog clocks</span></a></li> <li class="toclevel-3 tocsection-24"><a href="#Digital_clocks"><span class="tocnumber">4.1.2</span> <span class="toctext">Digital clocks</span></a></li> <li class="toclevel-3 tocsection-25"><a href="#Auditory_clocks"><span class="tocnumber">4.1.3</span> <span class="toctext">Auditory clocks</span></a></li> <li class="toclevel-3 tocsection-26"><a href="#Word_clocks"><span class="tocnumber">4.1.4</span> <span class="toctext">Word clocks</span></a></li> <li class="toclevel-3 tocsection-27"><a href="#Projection_clocks"><span class="tocnumber">4.1.5</span> <span class="toctext">Projection clocks</span></a></li> <li class="toclevel-3 tocsection-28"><a href="#Tactile_clocks"><span class="tocnumber">4.1.6</span> <span class="toctext">Tactile clocks</span></a></li> <li class="toclevel-3 tocsection-29"><a href="#Multi-display_clocks"><span class="tocnumber">4.1.7</span> <span class="toctext">Multi-display clocks</span></a></li> </ul> </li> </ul> </li> <li class="toclevel-1 tocsection-30"><a href="#Purposes"><span class="tocnumber">5</span> <span class="toctext">Purposes</span></a> <ul> <li class="toclevel-2 tocsection-31"><a href="#Time_standards"><span class="tocnumber">5.1</span> <span class="toctext">Time standards</span></a></li> <li class="toclevel-2 tocsection-32"><a href="#Navigation"><span class="tocnumber">5.2</span> <span class="toctext">Navigation</span></a></li> <li class="toclevel-2 tocsection-33"><a href="#Seismology"><span class="tocnumber">5.3</span> <span class="toctext">Seismology</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-34"><a href="#Specific_types_of_clocks"><span class="tocnumber">6</span> <span class="toctext">Specific types of clocks</span></a></li> <li class="toclevel-1 tocsection-35"><a href="#See_also"><span class="tocnumber">7</span> <span class="toctext">See also</span></a> <ul> <li class="toclevel-2 tocsection-36"><a href="#Newsgroup"><span class="tocnumber">7.1</span> <span class="toctext">Newsgroup</span></a></li> </ul> </li> <li class="toclevel-1 tocsection-37"><a href="#Notes_and_references"><span class="tocnumber">8</span> <span class="toctext">Notes and references</span></a></li> <li class="toclevel-1 tocsection-38"><a href="#Bibliography"><span class="tocnumber">9</span> <span class="toctext">Bibliography</span></a></li> <li class="toclevel-1 tocsection-39"><a href="#External_links"><span class="tocnumber">10</span> <span class="toctext">External links</span></a></li> </ul> </div> <p></p> <h2><span class="mw-headline" id="History">History</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=1" title="Edit section: History">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <div class="hatnote relarticle mainarticle">Main article: <a href="/web/20150320193459/https://en.wikipedia.org/wiki/History_of_timekeeping_devices" title="History of timekeeping devices">History of timekeeping devices</a></div> <h2><span class="mw-headline" id="Time-measuring_devices">Time-measuring devices</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=2" title="Edit section: Time-measuring devices">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <h3><span class="mw-headline" id="Sundials">Sundials</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=3" title="Edit section: Sundials">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="thumb tright"> <div class="thumbinner" style="width:152px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Garden_sundial_MN_2007.JPG" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Garden_sundial_MN_2007.JPG/150px-Garden_sundial_MN_2007.JPG" width="150" height="113" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Garden_sundial_MN_2007.JPG/225px-Garden_sundial_MN_2007.JPG 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/75/Garden_sundial_MN_2007.JPG/300px-Garden_sundial_MN_2007.JPG 2x" data-file-width="2576" data-file-height="1932"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Garden_sundial_MN_2007.JPG" class="internal" title="Enlarge"></a></div> Simple horizontal sundial</div> </div> </div> <p>When the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sun" title="Sun">Sun</a> is shining, its apparent position in the sky moves during a day, reflecting the rotation of the Earth. Shadows cast by stationary objects move correspondingly, so their positions can be used to indicate the time of day. A <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sundial" title="Sundial">sundial</a> shows the time by displaying the position of a shadow on a (usually) flat surface, which has markings that correspond to the hours.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span>[</span>7<span>]</span></a></sup> Sundials can be horizontal, vertical, or in other orientations. Sundials were widely used in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Ancient_history" title="Ancient history">ancient times</a>.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span>[</span>8<span>]</span></a></sup> With the knowledge of latitude, a well-constructed sundial can measure local <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_time" title="Solar time">solar time</a> with reasonable accuracy, within a minute or two. Sundials continued to be used to monitor the performance of clocks until the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Modern_era" title="Modern era" class="mw-redirect">modern era</a>.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (November 2014)">citation needed</span></a></i>]</sup> However, practical limitations, such as that sundials work only when the Sun shines, and never during the night, encouraged the use of other techniques for measuring and displaying time.</p> <h3><span class="mw-headline" id="Devices_that_measure_duration.2C_elapsed_time_and.2For_intervals">Devices that measure duration, elapsed time and/or intervals</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=4" title="Edit section: Devices that measure duration, elapsed time and/or intervals">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="thumb tright"> <div class="thumbinner" style="width:152px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Wooden_hourglass_3.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Wooden_hourglass_3.jpg/150px-Wooden_hourglass_3.jpg" width="150" height="304" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Wooden_hourglass_3.jpg/225px-Wooden_hourglass_3.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Wooden_hourglass_3.jpg/300px-Wooden_hourglass_3.jpg 2x" data-file-width="967" data-file-height="1959"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Wooden_hourglass_3.jpg" class="internal" title="Enlarge"></a></div> The flow of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sand" title="Sand">sand</a> in an <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hourglass" title="Hourglass">hourglass</a> can be used to keep track of elapsed time.</div> </div> </div> <p>Many devices can be used to mark passage of time without respect to reference time (time of day, minutes, etc...) and can be useful for measuring duration and/or intervals. Examples of such duration timers are, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Candle_clock" title="Candle clock">candle clocks</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Incense_clock" title="Incense clock">incense clocks</a> and the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hourglass" title="Hourglass">hourglass</a>. Both the candle clock and the incense clock work on the same principle wherein the consumption of resources is more or less constant allowing reasonably precise, and repeatable, estimates of time passages. In the hourglass, fine <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sand" title="Sand">sand</a> pouring through a tiny hole at a constant rate indicates an arbitrary, predetermined, passage of time, the resource is not consumed but re-used.</p> <h3><span class="mw-headline" id="Water_clocks">Water clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=5" title="Edit section: Water clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="hatnote relarticle mainarticle">Main article: <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Water_Clock" title="Water Clock" class="mw-redirect">Water Clock</a></div> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:SuSongClock1.JPG" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/d/db/SuSongClock1.JPG/220px-SuSongClock1.JPG" width="220" height="359" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/d/db/SuSongClock1.JPG/330px-SuSongClock1.JPG 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/d/db/SuSongClock1.JPG 2x" data-file-width="384" data-file-height="627"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:SuSongClock1.JPG" class="internal" title="Enlarge"></a></div> A <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Scale_model" title="Scale model">scale model</a> of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Su_Song" title="Su Song">Su Song</a>'s <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astronomical" title="Astronomical" class="mw-redirect">Astronomical</a> Clock Tower, built in 11th century <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Kaifeng" title="Kaifeng">Kaifeng</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/China" title="China">China</a>. It was driven by a large <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Waterwheel" title="Waterwheel" class="mw-redirect">waterwheel</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chain_drive" title="Chain drive">chain drive</a>, and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Escapement" title="Escapement">escapement</a> mechanism.</div> </div> </div> <p>Water clocks, also known as clepsydrae (sg: <i>clepsydra</i>), along with the sundials, are possibly the oldest time-measuring instruments, with the only exceptions being the vertical <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gnomon" title="Gnomon">gnomon</a> and the day counting <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tally_stick" title="Tally stick">tally stick</a>.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span>[</span>9<span>]</span></a></sup> Given their great antiquity, where and when they first existed is not known and perhaps unknowable. The bowl-shaped outflow is the simplest form of a water clock and is known to have existed in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Babylon" title="Babylon">Babylon</a> and in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Egypt" title="Egypt">Egypt</a> around the 16th century BC. Other regions of the world, including <a href="/web/20150320193459/https://en.wikipedia.org/wiki/India" title="India">India</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/China" title="China">China</a>, also have early evidence of water clocks, but the earliest dates are less certain. Some authors, however, write about water clocks appearing as early as 4000 BC in these regions of the world.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span>[</span>10<span>]</span></a></sup></p> <p><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Ancient_Greece" title="Ancient Greece">Greek</a> astronomer <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Andronicus_of_Cyrrhus" title="Andronicus of Cyrrhus">Andronicus of Cyrrhus</a> supervised the construction of the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tower_of_the_Winds" title="Tower of the Winds">Tower of the Winds</a> in Athens in the 1st century B.C.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span>[</span>11<span>]</span></a></sup></p> <p>The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Ancient_Greece" title="Ancient Greece">Greek</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Ancient_Rome" title="Ancient Rome">Roman</a> civilizations are credited for initially advancing water clock design to include complex <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gear" title="Gear">gearing</a>, which was connected to fanciful <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Automaton" title="Automaton">automata</a> and also resulted in improved accuracy. These advances were passed on through <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Byzantium" title="Byzantium">Byzantium</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Islamic" title="Islamic" class="mw-redirect">Islamic</a> times, eventually making their way back to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Europe" title="Europe">Europe</a>. Independently, the Chinese developed their own advanced water clocks（水鐘）in 725 A.D., passing their ideas on to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Korea" title="Korea">Korea</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Japan" title="Japan">Japan</a>.</p> <div class="thumb tleft"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Clock_of_al_Jazari_before_1206.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Clock_of_al_Jazari_before_1206.jpg/220px-Clock_of_al_Jazari_before_1206.jpg" width="220" height="285" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Clock_of_al_Jazari_before_1206.jpg/330px-Clock_of_al_Jazari_before_1206.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/3/3d/Clock_of_al_Jazari_before_1206.jpg 2x" data-file-width="384" data-file-height="497"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Clock_of_al_Jazari_before_1206.jpg" class="internal" title="Enlarge"></a></div> Automatic clock of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Al-Jazari" title="Al-Jazari">al-Jazari</a>, 14th century.</div> </div> </div> <p>Some water clock designs were developed independently and some knowledge was transferred through the spread of trade. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pre-modern" title="Pre-modern" class="mw-redirect">Pre-modern</a> societies do not have the same precise timekeeping requirements that exist in modern <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Industrialism" title="Industrialism" class="mw-redirect">industrial</a> societies, where every hour of work or rest is monitored, and work may start or finish at any time regardless of external conditions. Instead, water clocks in ancient societies were used mainly for <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astrology" title="Astrology">astrological</a> reasons. These early water clocks were calibrated with a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sundial" title="Sundial">sundial</a>. While never reaching the level of accuracy of a modern timepiece, the water clock was the most accurate and commonly used timekeeping device for millennia, until it was replaced by the more accurate <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pendulum_clock" title="Pendulum clock">pendulum clock</a> in 17th-century Europe.</p> <p>Islamic civilization is credited with further advancing the accuracy of clocks with elaborate engineering. In 797 (or possibly 801), the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Abbasid" title="Abbasid" class="mw-redirect">Abbasid</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Caliph" title="Caliph" class="mw-redirect">caliph</a> of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Baghdad" title="Baghdad">Baghdad</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Harun_al-Rashid" title="Harun al-Rashid">Harun al-Rashid</a>, presented <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Charlemagne" title="Charlemagne">Charlemagne</a> with an <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Asian_Elephant" title="Asian Elephant" class="mw-redirect">Asian Elephant</a> named <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Abul-Abbas" title="Abul-Abbas">Abul-Abbas</a> together with a "particularly elaborate example" of a water<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span>[</span>12<span>]</span></a></sup> clock.</p> <p><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pope_Sylvester_II" title="Pope Sylvester II">Pope Sylvester II</a> introduced clocks to northern and western Europe around 1000 C.E.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span>[</span>13<span>]</span></a></sup></p> <div class="thumb tright"> <div class="thumbinner" style="width:202px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Al-jazari_elephant_clock.png" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Al-jazari_elephant_clock.png/200px-Al-jazari_elephant_clock.png" width="200" height="313" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Al-jazari_elephant_clock.png/300px-Al-jazari_elephant_clock.png 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/76/Al-jazari_elephant_clock.png/400px-Al-jazari_elephant_clock.png 2x" data-file-width="1013" data-file-height="1587"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Al-jazari_elephant_clock.png" class="internal" title="Enlarge"></a></div> An <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Elephant_clock" title="Elephant clock">elephant clock</a> in a manuscript by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Al-Jazari" title="Al-Jazari">Al-Jazari</a> (1206 AD) from <i>The Book of Knowledge of Ingenious Mechanical Devices</i>.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span>[</span>14<span>]</span></a></sup></div> </div> </div> <p>In the 13th century, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Al-Jazari" title="Al-Jazari">Al-Jazari</a>, an engineer from Mesopotamia (lived 1136-1206) who worked for <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Artuqid" title="Artuqid" class="mw-redirect">Artuqid</a> king of Diyar-Bakr, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Nasrudin" title="Nasrudin" class="mw-redirect">Nasir al-Din</a>, made numerous clocks of all shapes and sizes. The book described 50 mechanical devices in 6 categories, including water clocks. The most reputed clocks included <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Elephant_clock" title="Elephant clock">the Elephant</a>, Scribe and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Castle_clock" title="Castle clock" class="mw-redirect">Castle clocks</a>, all of which have been successfully reconstructed. As well as telling the time, these grand clocks were symbols of status, grandeur and wealth of the Urtuq State.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (May 2010)">citation needed</span></a></i>]</sup></p> <h3><span class="mw-headline" id="Early_mechanical_clocks">Early mechanical clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=6" title="Edit section: Early mechanical clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>The word <i>horologia</i> (from the Greek ὡρα, hour, and λέγειν, to tell) was used to describe early mechanical clocks,<sup id="cite_ref-wmsmith1875_15-0" class="reference"><a href="#cite_note-wmsmith1875-15"><span>[</span>15<span>]</span></a></sup> but the use of this word (still used in several <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Romance_languages" title="Romance languages">Romance languages</a>) <sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span>[</span>16<span>]</span></a></sup> for all timekeepers conceals the true nature of the mechanisms. For example, there is a record that in 1176 <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cath%C3%A9drale_Saint-%C3%89tienne_de_Sens" title="Cathédrale Saint-Étienne de Sens" class="mw-redirect">Sens Cathedral</a> installed a ‘<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Horologe" title="Horologe" class="mw-redirect">horologe</a>’<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span>[</span>17<span>]</span></a></sup> but the mechanism used is unknown. According to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Jocelin_of_Brakelond" title="Jocelin of Brakelond" class="mw-redirect">Jocelin of Brakelond</a>, in 1198 during a fire at the abbey of St Edmundsbury (now <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Bury_St_Edmunds" title="Bury St Edmunds">Bury St Edmunds</a>), the monks 'ran to the clock' to fetch water, indicating that their water clock had a reservoir large enough to help extinguish the occasional fire.<sup id="cite_ref-18" class="reference"><a href="#cite_note-18"><span>[</span>18<span>]</span></a></sup></p> <p>The word <i>clock</i> (from the Celtic words <i>clocca</i> and <i>clogan</i>, both meaning "bell"), which gradually supersedes "horologe", suggests that it was the sound of bells which also characterized the prototype mechanical clocks that appeared during the 13th century in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Europe" title="Europe">Europe</a>.</p> <p>Outside Europe, the first mechanical clock was completed in China in AD 725 by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Yi_Xing" title="Yi Xing">Yi Xing</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Liang_Lingzan" title="Liang Lingzan">Liang Lingzan</a>.<sup id="cite_ref-19" class="reference"><a href="#cite_note-19"><span>[</span>19<span>]</span></a></sup> The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Escapement" title="Escapement">escapement</a> mechanism had been known and used in medieval China, as the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Song_Dynasty" title="Song Dynasty" class="mw-redirect">Song Dynasty</a> horologist and engineer <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Su_Song" title="Su Song">Su Song</a> (1020–1101) incorporated it into his astronomical clock-tower of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Kaifeng" title="Kaifeng">Kaifeng</a> in 1088.<sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span>[</span>20<span>]</span></a></sup><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Citing_sources" title="Wikipedia:Citing sources"><span title="This citation requires a reference to the specific page or range of pages in which the material appears. (July 2011)">page needed</span></a></i>]</sup> His astronomical clock and rotating <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Armillary_sphere" title="Armillary sphere">armillary sphere</a> still relied on the use of flowing water (i.e. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hydraulics" title="Hydraulics">hydraulics</a>), while European clockworks of the following centuries shed this method for a more efficient driving power of weights, in addition to the escapement mechanism.</p> <p>A mercury clock, described in the <i>Libros del saber</i>, a Spanish work from 1277 consisting of translations and paraphrases of Arabic works, is sometimes quoted as evidence for Muslim knowledge of a mechanical clock. The first mercury powered automatic clock was invented by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Al-Muradi" title="Al-Muradi">Ibn Khalaf al-Muradi</a><sup id="cite_ref-Leonardo_21-0" class="reference"><a href="#cite_note-Leonardo-21"><span>[</span>21<span>]</span></a></sup><sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span>[</span>22<span>]</span></a></sup></p> <p>Between 1280 and 1320, there is an increase in the number of references to clocks and horologes in church records, and this probably indicates that a new type of clock mechanism had been devised. Existing clock mechanisms that used <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hydropower" title="Hydropower">water power</a> were being adapted to take their driving power from falling weights. This power was controlled by some form of oscillating mechanism, probably derived from existing bell-ringing or alarm devices. This controlled release of power—the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Escapement" title="Escapement">escapement</a>—marks the beginning of the true mechanical clock.</p> <p>These mechanical clocks were intended for two main purposes: for signalling and notification (e.g. the timing of services and public events), and for modeling the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_system" title="Solar system" class="mw-redirect">solar system</a>. The former purpose is administrative, the latter arises naturally given the scholarly interests in astronomy, science, astrology, and how these subjects integrated with the religious philosophy of the time. The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astrolabe" title="Astrolabe">astrolabe</a> was used both by astronomers and astrologers, and it was natural to apply a clockwork drive to the rotating plate to produce a working model of the solar system.</p> <p>Simple clocks intended mainly for notification were installed in towers, and did not always require faces or hands. They would have announced the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Canonical_hours" title="Canonical hours">canonical hours</a> or intervals between set times of prayer. Canonical hours varied in length as the times of sunrise and sunset shifted. The more sophisticated astronomical clocks would have had moving dials or hands, and would have shown the time in various time systems, including <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hour#Counting_from_sunset" title="Hour">Italian hours</a>, canonical hours, and time as measured by astronomers at the time. Both styles of clock started acquiring extravagant features such as <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Automata" title="Automata" class="mw-redirect">automata</a>.</p> <p>In 1283, a large clock was installed at <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Dunstable_Priory" title="Dunstable Priory">Dunstable Priory</a>; its location above the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Rood_screen" title="Rood screen">rood screen</a> suggests that it was not a water clock.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (October 2007)">citation needed</span></a></i>]</sup> In 1292, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Canterbury_Cathedral" title="Canterbury Cathedral">Canterbury Cathedral</a> installed a 'great horloge'. Over the next 30 years there are mentions of clocks at a number of ecclesiastical institutions in England, Italy, and France. In 1322, a new clock was installed in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Norwich" title="Norwich">Norwich</a>, an expensive replacement for an earlier clock installed in 1273. This had a large (2 metre) astronomical dial with automata and bells. The costs of the installation included the full-time employment of two <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clockkeeper" title="Clockkeeper">clockkeepers</a> for two years.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (October 2007)">citation needed</span></a></i>]</sup></p> <h3><span class="mw-headline" id="Astronomical_clocks">Astronomical clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=7" title="Edit section: Astronomical clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Abbot_Richard_Wallingford.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Abbot_Richard_Wallingford.jpg/220px-Abbot_Richard_Wallingford.jpg" width="220" height="236" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Abbot_Richard_Wallingford.jpg/330px-Abbot_Richard_Wallingford.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/f/f2/Abbot_Richard_Wallingford.jpg/440px-Abbot_Richard_Wallingford.jpg 2x" data-file-width="696" data-file-height="748"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Abbot_Richard_Wallingford.jpg" class="internal" title="Enlarge"></a></div> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Richard_of_Wallingford" title="Richard of Wallingford">Richard of Wallingford</a> pointing to a clock, his gift to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/St_Albans_Abbey" title="St Albans Abbey" class="mw-redirect">St Albans Abbey</a></div> </div> </div> <p>Besides the Chinese astronomical clock of Su Song in 1088 mentioned above, in Europe there were the clocks constructed by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Richard_of_Wallingford" title="Richard of Wallingford">Richard of Wallingford</a> in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/St_Albans" title="St Albans">St Albans</a> by 1336, and by Giovanni <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Giovanni_Dondi_dell%27Orologio" title="Giovanni Dondi dell'Orologio">de Dondi</a> in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Padua,_Italy" title="Padua, Italy" class="mw-redirect">Padua</a> from 1348 to 1364. They no longer exist, but detailed descriptions of their design and construction survive,<sup id="cite_ref-north_23-0" class="reference"><a href="#cite_note-north-23"><span>[</span>23<span>]</span></a></sup><sup id="cite_ref-king_24-0" class="reference"><a href="#cite_note-king-24"><span>[</span>24<span>]</span></a></sup> and modern reproductions have been made.<sup id="cite_ref-king_24-1" class="reference"><a href="#cite_note-king-24"><span>[</span>24<span>]</span></a></sup> They illustrate how quickly the theory of the mechanical clock had been translated into practical constructions, and also that one of the many impulses to their development had been the desire of astronomers to investigate celestial phenomena.</p> <p>Wallingford's clock had a large astrolabe-type dial, showing the sun, the moon's age, phase, and node, a star map, and possibly the planets. In addition, it had a wheel of fortune and an indicator of the state of the tide at <a href="/web/20150320193459/https://en.wikipedia.org/wiki/London_Bridge" title="London Bridge">London Bridge</a>. Bells rang every hour, the number of strokes indicating the time.<sup id="cite_ref-north_23-1" class="reference"><a href="#cite_note-north-23"><span>[</span>23<span>]</span></a></sup></p> <p>Dondi's clock was a seven-sided construction, 1 metre high, with dials showing the time of day, including minutes, the motions of all the known planets, an automatic calendar of fixed and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Moveable_feast" title="Moveable feast">movable feasts</a>, and an eclipse prediction hand rotating once every 18 years.<sup id="cite_ref-king_24-2" class="reference"><a href="#cite_note-king-24"><span>[</span>24<span>]</span></a></sup></p> <p>It is not known how accurate or reliable these clocks would have been. They were probably adjusted manually every day to compensate for errors caused by wear and imprecise manufacture. Water clocks are sometimes still used today, and can be examined in places such as ancient castles and museums.</p> <p>The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Salisbury_cathedral_clock" title="Salisbury cathedral clock">Salisbury Cathedral clock</a>, built in 1386, is considered to be the world's oldest surviving mechanical clock that strikes the hours.<sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span>[</span>25<span>]</span></a></sup></p> <h3><span class="mw-headline" id="Spring-driven_clocks">Spring-driven clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=8" title="Edit section: Spring-driven clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Henlein_Taschenuhr.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/65/Henlein_Taschenuhr.jpg/220px-Henlein_Taschenuhr.jpg" width="220" height="229" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/65/Henlein_Taschenuhr.jpg/330px-Henlein_Taschenuhr.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/65/Henlein_Taschenuhr.jpg/440px-Henlein_Taschenuhr.jpg 2x" data-file-width="1818" data-file-height="1893"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Henlein_Taschenuhr.jpg" class="internal" title="Enlarge"></a></div> One of the first pocket watches, called "Nuremberg Egg", made around 1510 and attributed to Peter Henlein, (Germanisches Nationalmuseum, Nuremberg)</div> </div> </div> <p>Clockmakers developed their art in various ways. Building smaller clocks was a technical challenge, as was improving accuracy and reliability. Clocks could be impressive showpieces to demonstrate skilled craftsmanship, or less expensive, mass-produced items for domestic use. The escapement in particular was an important factor affecting the clock's accuracy, so many different mechanisms were tried.</p> <p>Spring-driven clocks appeared during the 15th century,<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span>[</span>26<span>]</span></a></sup><sup id="cite_ref-White_6-1" class="reference"><a href="#cite_note-White-6"><span>[</span>6<span>]</span></a></sup><sup id="cite_ref-Rossum_27-0" class="reference"><a href="#cite_note-Rossum-27"><span>[</span>27<span>]</span></a></sup> although they are often erroneously credited to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Nuremberg" title="Nuremberg">Nuremberg</a> watchmaker <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Peter_Henlein" title="Peter Henlein">Peter Henlein</a> (or Henle, or Hele) around 1511.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span>[</span>28<span>]</span></a></sup><sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span>[</span>29<span>]</span></a></sup><sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span>[</span>30<span>]</span></a></sup> The earliest existing spring driven clock is the chamber clock given to Phillip the Good, Duke of Burgundy, around 1430, now in the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Germanisches_Nationalmuseum" title="Germanisches Nationalmuseum">Germanisches Nationalmuseum</a>.<sup id="cite_ref-White_6-2" class="reference"><a href="#cite_note-White-6"><span>[</span>6<span>]</span></a></sup> Spring power presented clockmakers with a new problem: how to keep the clock <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Movement_(clockwork)" title="Movement (clockwork)">movement</a> running at a constant rate as the spring ran down. This resulted in the invention of the <i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Stackfreed" title="Stackfreed">stackfreed</a></i> and the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Fusee_(horology)" title="Fusee (horology)">fusee</a> in the 15th century, and many other innovations, down to the invention of the modern <i>going <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Barrel_(horology)" title="Barrel (horology)">barrel</a></i> in 1760.</p> <p>Early clock dials did not indicate minutes and seconds. A clock with a dial indicating minutes was illustrated in a 1475 manuscript by Paulus Almanus,<sup id="cite_ref-haencyc_31-0" class="reference"><a href="#cite_note-haencyc-31"><span>[</span>31<span>]</span></a></sup> and some 15th-century clocks in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Germany" title="Germany">Germany</a> indicated minutes and seconds.<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span>[</span>32<span>]</span></a></sup> An early record of a seconds hand on a clock dates back to about 1560 on a clock now in the Fremersdorf collection.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (October 2007)">citation needed</span></a></i>]</sup></p> <p>During the 15th and 16th centuries, clockmaking flourished, particularly in the metalworking towns of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Nuremberg" title="Nuremberg">Nuremberg</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Augsburg" title="Augsburg">Augsburg</a>, and in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Blois" title="Blois">Blois</a>, France. Some of the more basic table clocks have only one time-keeping hand, with the dial between the hour markers being divided into four equal parts making the clocks readable to the nearest 15 minutes. Other clocks were exhibitions of craftsmanship and skill, incorporating astronomical indicators and musical movements. The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Escapement#Cross-beat_escapement" title="Escapement">cross-beat escapement</a> was invented in 1584 by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Jost_B%C3%BCrgi" title="Jost Bürgi">Jost Bürgi</a>, who also developed the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Remontoire" title="Remontoire">remontoire</a>. Bürgi's clocks were a great improvement in accuracy as they were correct to within a minute a day.<sup id="cite_ref-33" class="reference"><a href="#cite_note-33"><span>[</span>33<span>]</span></a></sup><sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span>[</span>34<span>]</span></a></sup> These clocks helped the 16th-century astronomer <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tycho_Brahe" title="Tycho Brahe">Tycho Brahe</a> to observe astronomical events with much greater precision than before.<sup class="noprint Inline-Template Template-Fact" style="white-space:nowrap;">[<i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Citation_needed" title="Wikipedia:Citation needed"><span title="This claim needs references to reliable sources. (November 2014)">citation needed</span></a></i>]</sup><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Please_clarify" title="Wikipedia:Please clarify"><span title="Please clarify the following statement or statements with a good explanation from a reliable source. (November 2014)">how?</span></a></i>]</sup></p> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Mus%C3%A9e_du_temps_Besan%C3%A7on_3.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Mus%C3%A9e_du_temps_Besan%C3%A7on_3.jpg/220px-Mus%C3%A9e_du_temps_Besan%C3%A7on_3.jpg" width="220" height="165" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Mus%C3%A9e_du_temps_Besan%C3%A7on_3.jpg/330px-Mus%C3%A9e_du_temps_Besan%C3%A7on_3.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Mus%C3%A9e_du_temps_Besan%C3%A7on_3.jpg/440px-Mus%C3%A9e_du_temps_Besan%C3%A7on_3.jpg 2x" data-file-width="1024" data-file-height="768"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Mus%C3%A9e_du_temps_Besan%C3%A7on_3.jpg" class="internal" title="Enlarge"></a></div> French <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Rococo" title="Rococo">rococo</a> bracket clocks (Museum of Time, Besançon).</div> </div> </div> <h3><span class="mw-headline" id="Pendulum_clock">Pendulum clock</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=9" title="Edit section: Pendulum clock">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Reloj_de_pendulo_Ansonia_C-1904.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/2/22/Reloj_de_pendulo_Ansonia_C-1904.jpg/220px-Reloj_de_pendulo_Ansonia_C-1904.jpg" width="220" height="412" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/2/22/Reloj_de_pendulo_Ansonia_C-1904.jpg/330px-Reloj_de_pendulo_Ansonia_C-1904.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/2/22/Reloj_de_pendulo_Ansonia_C-1904.jpg/440px-Reloj_de_pendulo_Ansonia_C-1904.jpg 2x" data-file-width="1648" data-file-height="3088"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Reloj_de_pendulo_Ansonia_C-1904.jpg" class="internal" title="Enlarge"></a></div> Pendulum clock Ansonia. C.1904, Ansonia Clock Co., SANTIAGO, hanging oak gingerbread clock, 8-day time and strike.</div> </div> </div> <p>The next development in accuracy occurred after 1656 with the invention of the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pendulum_clock" title="Pendulum clock">pendulum clock</a>. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Galileo_Galilei" title="Galileo Galilei">Galileo</a> had the idea to use a swinging bob to regulate the motion of a time-telling device earlier in the 17th century. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Christiaan_Huygens" title="Christiaan Huygens">Christiaan Huygens</a>, however, is usually credited as the inventor. He determined the mathematical formula that related pendulum length to time (99.38 cm or 39.13 inches for the one second movement) and had the first pendulum-driven clock made. The first model clock was built in 1657 in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/The_Hague" title="The Hague">the Hague</a>, but it was in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/England" title="England">England</a> that the idea was taken up.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span>[</span>35<span>]</span></a></sup> The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Longcase_clock" title="Longcase clock">longcase clock</a> (also known as the <i>grandfather clock</i>) was created to house the pendulum and works by the English clockmaker William Clement in 1670 or 1671. It was also at this time that clock cases began to be made of wood and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_face" title="Clock face">clock faces</a> to utilize <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Vitreous_enamel" title="Vitreous enamel">enamel</a> as well as hand-painted ceramics.</p> <p>In 1670, William Clement created the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Anchor_escapement" title="Anchor escapement">anchor escapement</a>,<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span>[</span>36<span>]</span></a></sup> an improvement over Huygens' crown escapement. Clement also introduced the pendulum suspension spring in 1671. The concentric minute hand was added to the clock by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Daniel_Quare" title="Daniel Quare">Daniel Quare</a>, a London clock-maker and others, and the Second Hand was first introduced.</p> <h3><span class="mw-headline" id="Hairspring">Hairspring</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=10" title="Edit section: Hairspring">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>In 1675, Huygens and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Robert_Hooke" title="Robert Hooke">Robert Hooke</a> invented the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Spiral_balance" title="Spiral balance" class="mw-redirect">spiral balance</a>, or the hairspring, designed to control the oscillating speed of the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Balance_wheel" title="Balance wheel">balance wheel</a>. This crucial advance finally made accurate pocket watches possible. The great English clockmaker, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Thomas_Tompion" title="Thomas Tompion">Thomas Tompion</a>, was one of the first to use this mechanism successfully in his <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pocket_watch" title="Pocket watch">pocket watches</a>, and he adopted the minute hand which, after a variety of designs were trialled, eventually stabilised into the modern-day configuration.<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span>[</span>37<span>]</span></a></sup></p> <p>The Rev. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Edward_Barlow_(priest)" title="Edward Barlow (priest)">Edward Barlow</a> invented the rack and snail striking mechanism for <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Striking_clock" title="Striking clock">striking clocks</a>, which was a great improvement over the previous mechanism. The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Repeater_(horology)" title="Repeater (horology)">repeating clock</a>, that chimes the number of hours (or even minutes) was invented by either Quare or Barlow in 1676. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/George_Graham_(clockmaker)" title="George Graham (clockmaker)">George Graham</a> invented the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Escapement#Deadbeat_escapement" title="Escapement">deadbeat escapement</a> for clocks in 1720.</p> <h3><span class="mw-headline" id="Marine_chronometer">Marine chronometer</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=11" title="Edit section: Marine chronometer">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Harrison_H4_clock_in_The_principles_of_Mr_Harrison%27s_time-keeper_1767.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Harrison_H4_clock_in_The_principles_of_Mr_Harrison%27s_time-keeper_1767.jpg/220px-Harrison_H4_clock_in_The_principles_of_Mr_Harrison%27s_time-keeper_1767.jpg" width="220" height="326" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Harrison_H4_clock_in_The_principles_of_Mr_Harrison%27s_time-keeper_1767.jpg/330px-Harrison_H4_clock_in_The_principles_of_Mr_Harrison%27s_time-keeper_1767.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Harrison_H4_clock_in_The_principles_of_Mr_Harrison%27s_time-keeper_1767.jpg/440px-Harrison_H4_clock_in_The_principles_of_Mr_Harrison%27s_time-keeper_1767.jpg 2x" data-file-width="595" data-file-height="881"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Harrison_H4_clock_in_The_principles_of_Mr_Harrison%27s_time-keeper_1767.jpg" class="internal" title="Enlarge"></a></div> Drawings of Harrison's H4 chronometer of 1761, published in <i>The principles of Mr Harrison's time-keeper</i>, 1767.<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span>[</span>38<span>]</span></a></sup></div> </div> </div> <p>A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time-keeping for navigation. The position of a ship at sea could be determined with reasonable accuracy if a navigator could refer to a clock that lost or gained less than about 10 seconds per day. This clock could not contain a pendulum, which would be virtually useless on a rocking ship. In 1714, the British government offered a large <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Longitude_prize" title="Longitude prize">prize</a> to the value of 20,000 pounds,<sup id="cite_ref-Rigden2003_39-0" class="reference"><a href="#cite_note-Rigden2003-39"><span>[</span>39<span>]</span></a></sup> for anyone who could determine longitude accurately after the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Scilly_naval_disaster_of_1707" title="Scilly naval disaster of 1707">Scilly naval disaster of 1707</a>. The reward was eventually claimed in 1761 by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/John_Harrison" title="John Harrison">John Harrison</a>, who dedicated his life to improving the accuracy of his clocks.</p> <div class="thumb tleft"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Harrison%27s_Chronometer_H5.JPG" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Harrison%27s_Chronometer_H5.JPG/220px-Harrison%27s_Chronometer_H5.JPG" width="220" height="146" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Harrison%27s_Chronometer_H5.JPG/330px-Harrison%27s_Chronometer_H5.JPG 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Harrison%27s_Chronometer_H5.JPG/440px-Harrison%27s_Chronometer_H5.JPG 2x" data-file-width="3008" data-file-height="2000"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Harrison%27s_Chronometer_H5.JPG" class="internal" title="Enlarge"></a></div> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/John_Harrison" title="John Harrison">John Harrison</a>'s Chronometer H5</div> </div> </div> <p>In 1735, Harrison built his first chronometer, which he steadily improved on over the next thirty years before submitting it for examination. The clock had many innovations, including the use of bearings to reduce friction, weighted balances to compensate for the ship's pitch and roll in the sea and the use of two different metals to reduce the problem of expansion from heat.</p> <p>The chronometer was tested in 1761 by Harrison's son and by the end of 10 weeks the clock was in error by less than 5 seconds.<sup id="cite_ref-gould_40-0" class="reference"><a href="#cite_note-gould-40"><span>[</span>40<span>]</span></a></sup></p> <h3><span class="mw-headline" id="Mass_production">Mass production</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=12" title="Edit section: Mass production">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>The British had predominated in watch manufacture for much of the 17th and 18th centuries, but maintained a system of production that was geared towards high quality products for the elite.<sup id="cite_ref-41" class="reference"><a href="#cite_note-41"><span>[</span>41<span>]</span></a></sup> Although there was an attempt to modernise clock manufacture with <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mass_production" title="Mass production">mass production</a> techniques and the application of duplicating tools and machinery by the British Watch Company in 1843, it was in the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/United_States" title="United States">United States</a> that this system took off. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Aaron_Lufkin_Dennison" title="Aaron Lufkin Dennison">Aaron Lufkin Dennison</a> started a factory in 1851 in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Massachusetts" title="Massachusetts">Massachusetts</a> that used <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Interchangeable_parts" title="Interchangeable parts">interchangeable parts</a>, and by 1861 was running a successful enterprise incorporated as the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Waltham_Watch_Company" title="Waltham Watch Company">Waltham Watch Company</a>.<sup id="cite_ref-Roe1916_42-0" class="reference"><a href="#cite_note-Roe1916-42"><span>[</span>42<span>]</span></a></sup><sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span>[</span>43<span>]</span></a></sup></p> <h3><span class="mw-headline" id="Electric_clocks">Electric clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=13" title="Edit section: Electric clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Alexander_Bain_(inventor)" title="Alexander Bain (inventor)">Alexander Bain</a>, Scottish clockmaker, patented the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electric_clock" title="Electric clock">electric clock</a> in 1840. The electric clock's mainspring is wound either with an <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electric_motor" title="Electric motor">electric motor</a> or with an <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electromagnet" title="Electromagnet">electromagnet</a> and armature. In 1841, he first patented the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electromagnetism" title="Electromagnetism">electromagnetic</a> pendulum.</p> <p>By the end of the nineteenth century, the advent of the dry cell battery made it feasible to use electric power in clocks. Spring or weight driven clocks that use electricity, either <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Alternating_current" title="Alternating current">alternating current</a> (AC) or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Direct_current" title="Direct current">direct current</a> (DC), to rewind the spring or raise the weight of a mechanical clock would be classified as an <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electromechanical_clock" title="Electromechanical clock" class="mw-redirect">electromechanical clock</a>. This classification would also apply to clocks that employ an electrical impulse to propel the pendulum. In electromechanical clocks the electricity serves no time keeping function. These types of clocks were made as individual timepieces but more commonly used in synchronized time installations in schools, businesses, factories, railroads and government facilities as a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Master_clock" title="Master clock">master clock</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Slave_clocks" title="Slave clocks" class="mw-redirect">slave clocks</a>.</p> <p>Electric clocks that are powered from the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Alternating_current" title="Alternating current">AC</a> supply often use <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Synchronous_motor" title="Synchronous motor">synchronous motors</a>. The supply current alternates with a frequency of exactly 50 <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hertz" title="Hertz">hertz</a> in many countries, and 60 hertz in others. The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Rotor_(electric)" title="Rotor (electric)">rotor</a> of the motor rotates at a speed that is exactly related to the alternation frequency. Appropriate gearing converts this rotation speed to the correct ones for the hands of the analog clock.</p> <p>The development of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electronics" title="Electronics">electronics</a> in the 20th century led to clocks with no clockwork parts at all. Time in these cases is measured in several ways, such as by the alternation of the AC supply, vibration of a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tuning_fork" title="Tuning fork">tuning fork</a>, the behaviour of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Quartz" title="Quartz">quartz</a> crystals, or the quantum vibrations of atoms. Electronic circuits divide these high-frequency oscillations to slower ones that drive the time display. Even mechanical clocks have since come to be largely powered by batteries, removing the need for winding.</p> <h2><span class="mw-headline" id="How_clocks_work">How clocks work</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=14" title="Edit section: How clocks work">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <p>The invention of the mechanical clock in the 13th century initiated a change in timekeeping methods from <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Continuous_function" title="Continuous function">continuous</a> processes, such as the motion of the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gnomon" title="Gnomon">gnomon</a>'s shadow on a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sundial" title="Sundial">sundial</a> or the flow of liquid in a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Water_clock" title="Water clock">water clock</a>, to periodic <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Oscillatory" title="Oscillatory" class="mw-redirect">oscillatory</a> processes, such as the swing of a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pendulum" title="Pendulum">pendulum</a> or the vibration of a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Crystal_oscillator" title="Crystal oscillator">quartz crystal</a>,<sup id="cite_ref-Cipolla_5-1" class="reference"><a href="#cite_note-Cipolla-5"><span>[</span>5<span>]</span></a></sup> which had the potential for more accuracy. All modern clocks use oscillation.</p> <p>Although the methods they use vary, all oscillating clocks, mechanical and digital and atomic, work similarly and can be divided into analogous parts.<sup id="cite_ref-Jespersen_44-0" class="reference"><a href="#cite_note-Jespersen-44"><span>[</span>44<span>]</span></a></sup><sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span>[</span>45<span>]</span></a></sup><sup id="cite_ref-Milham_46-0" class="reference"><a href="#cite_note-Milham-46"><span>[</span>46<span>]</span></a></sup> They consist of an object that repeats the same motion over and over again, an <i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Oscillator" title="Oscillator" class="mw-redirect">oscillator</a></i>, with a precisely constant time interval between each repetition, or 'beat'. Attached to the oscillator is a <i>controller</i> device, which sustains the oscillator's motion by replacing the energy it loses to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Friction" title="Friction">friction</a>, and converts its oscillations into a series of pulses. The pulses are then counted by some type of <i>counter</i>, and the number of counts is converted into convenient units, usually seconds, minutes, hours, etc. Finally some kind of <i>indicator</i> displays the result in human readable form.</p> <h3><span class="mw-headline" id="Power_source">Power source</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=15" title="Edit section: Power source">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Mainspring_wind-up_keys.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Mainspring_wind-up_keys.jpg/220px-Mainspring_wind-up_keys.jpg" width="220" height="137" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Mainspring_wind-up_keys.jpg/330px-Mainspring_wind-up_keys.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/7c/Mainspring_wind-up_keys.jpg/440px-Mainspring_wind-up_keys.jpg 2x" data-file-width="2872" data-file-height="1788"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Mainspring_wind-up_keys.jpg" class="internal" title="Enlarge"></a></div> Keys of various sizes for winding up mainsprings on clocks.</div> </div> </div> <p>This provides power to keep the clock going.</p> <ul> <li>In mechanical clocks, the power source is typically either a weight suspended from a cord or chain wrapped around a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pulley" title="Pulley">pulley</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sprocket" title="Sprocket">sprocket</a> or drum; or a spiral <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Spring_(device)" title="Spring (device)">spring</a> called a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mainspring" title="Mainspring">mainspring</a>. Mechanical clocks must be <i>wound</i> periodically, usually by turning a knob or key or by pulling on the free end of the chain, to store <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Energy" title="Energy">energy</a> in the weight or spring to keep the clock running.</li> <li>In <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electric_clock" title="Electric clock">electric clocks</a>, the power source is either a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Battery_(electricity)" title="Battery (electricity)">battery</a> or the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mains_power" title="Mains power" class="mw-redirect">AC power line</a>. In clocks that use AC power, a small <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Backup_battery" title="Backup battery">backup battery</a> is often included to keep the clock running if it is unplugged temporarily from the wall or during a power outage. Battery powered analog wall clocks are available that operate over 15 years between battery changes.</li> </ul> <h3><span class="mw-headline" id="Oscillator">Oscillator</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=16" title="Edit section: Oscillator">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>The timekeeping element in every modern clock is a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Harmonic_oscillator" title="Harmonic oscillator">harmonic oscillator</a>, a physical object (<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Resonator" title="Resonator">resonator</a>) that vibrates or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Oscillate" title="Oscillate" class="mw-redirect">oscillates</a> repetitively at a precisely constant <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Frequency" title="Frequency">frequency</a>.<sup id="cite_ref-Marrison_4-2" class="reference"><a href="#cite_note-Marrison-4"><span>[</span>4<span>]</span></a></sup></p> <ul> <li>In mechanical clocks, this is either a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pendulum" title="Pendulum">pendulum</a> or a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Balance_wheel" title="Balance wheel">balance wheel</a>.</li> <li>In some early electronic clocks and watches such as the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Accutron" title="Accutron" class="mw-redirect">Accutron</a>, it is a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tuning_fork" title="Tuning fork">tuning fork</a>.</li> <li>In <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Quartz_clock" title="Quartz clock">quartz clocks</a> and watches, it is a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Crystal_oscillator" title="Crystal oscillator">quartz crystal</a>.</li> <li>In <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">atomic clocks</a>, it is the vibration of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electron" title="Electron">electrons</a> in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atom" title="Atom">atoms</a> as they emit <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Microwave" title="Microwave">microwaves</a>.</li> <li>In early mechanical clocks before 1657, it was a crude balance wheel or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Verge_escapement" title="Verge escapement">foliot</a> which was not a harmonic oscillator because it lacked a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Balance_spring" title="Balance spring">balance spring</a>. As a result they were very inaccurate, with errors of perhaps an hour a day.<sup id="cite_ref-47" class="reference"><a href="#cite_note-47"><span>[</span>47<span>]</span></a></sup></li> </ul> <p>The advantage of a harmonic oscillator over other forms of oscillator is that it employs <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Resonance" title="Resonance">resonance</a> to vibrate at a precise natural <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Resonant_frequency" title="Resonant frequency" class="mw-redirect">resonant frequency</a> or 'beat' dependent only on its physical characteristics, and resists vibrating at other rates. The possible precision achievable by a harmonic oscillator is measured by a parameter called its <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Q_factor" title="Q factor">Q</a>,<sup id="cite_ref-48" class="reference"><a href="#cite_note-48"><span>[</span>48<span>]</span></a></sup><sup id="cite_ref-49" class="reference"><a href="#cite_note-49"><span>[</span>49<span>]</span></a></sup> or quality factor, which increases (other things being equal) with its resonant frequency.<sup id="cite_ref-50" class="reference"><a href="#cite_note-50"><span>[</span>50<span>]</span></a></sup> This is why there has been a long term trend toward higher frequency oscillators in clocks. Balance wheels and pendulums always include a means of adjusting the rate of the timepiece. Quartz timepieces sometimes include a rate screw that adjusts a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Capacitor" title="Capacitor">capacitor</a> for that purpose. Atomic clocks are <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Standard_(technical)" title="Standard (technical)" class="mw-redirect">primary standards</a>, and their rate cannot be adjusted.</p> <h4><span class="mw-headline" id="Synchronized_or_slave_clocks">Synchronized or slave clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=17" title="Edit section: Synchronized or slave clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h4> <p>Some clocks rely for their accuracy on an external oscillator; that is, they are automatically <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Synchronization" title="Synchronization">synchronized</a> to a more accurate clock:</p> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Slave_clock" title="Slave clock">Slave clocks</a>, used in large institutions and schools from the 1860s to the 1970s, kept time with a pendulum, but were wired to a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Master_clock" title="Master clock">master clock</a> in the building, and periodically received a signal to synchronize them with the master, often on the hour.<sup id="cite_ref-51" class="reference"><a href="#cite_note-51"><span>[</span>51<span>]</span></a></sup> Later versions without pendulums were triggered by a pulse from the master clock and certain sequences used to force rapid synchronization following a power failure.</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electric_clock" title="Electric clock">Synchronous electric clocks</a> do not have an internal oscillator, but count cycles of the 50 or 60 <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hertz" title="Hertz">Hz</a> oscillation of the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mains_power" title="Mains power" class="mw-redirect">AC power line</a>, which is synchronized by the utility to a precision oscillator. The counting may be done electronically, usually in clocks with digital displays, or, in analog clocks, the AC may drive a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Synchronous_motor" title="Synchronous motor">synchronous motor</a> which rotates an exact fraction of a revolution for every cycle of the line voltage, and drives the gear train. Although changes in the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electric_grid" title="Electric grid" class="mw-redirect">grid</a> line frequency due to load variations may cause the clock to temporarily gain or lose several seconds during the course of a day, the total number of cycles per 24 hours is maintained extremely accurately by the utility company, so that the clock keeps time accurately over long periods.</li> <li>Computer <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Real_time_clock" title="Real time clock" class="mw-redirect">real time clocks</a> keep time with a quartz crystal, but can be periodically (usually weekly) synchronized over the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Internet" title="Internet">Internet</a> to atomic clocks (<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UTC</a>), using the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Network_Time_Protocol" title="Network Time Protocol">Network Time Protocol</a> (NTP). Sometimes computers on a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Local_area_network" title="Local area network">local area network</a> (LAN) get their time from a single local server which is maintained accurately.</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Radio_clock" title="Radio clock">Radio clocks</a> keep time with a quartz crystal, but are periodically synchronized to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Radio_time_signal" title="Radio time signal" class="mw-redirect">time signals</a> transmitted from dedicated <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Radio_clock#List_of_radio_time_signal_stations" title="Radio clock">standard time radio stations</a> or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Satellite_navigation" title="Satellite navigation">satellite navigation</a> signals, which are set by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">atomic clocks</a>.</li> </ul> <h3><span class="mw-headline" id="Controller">Controller</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=18" title="Edit section: Controller">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>This has the dual function of keeping the oscillator running by giving it 'pushes' to replace the energy lost to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Friction" title="Friction">friction</a>, and converting its vibrations into a series of pulses that serve to measure the time.</p> <ul> <li>In mechanical clocks, this is the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Escapement" title="Escapement">escapement</a>, which gives precise pushes to the swinging pendulum or balance wheel, and releases one gear tooth of the <i>escape wheel</i> at each swing, allowing all the clock's wheels to move forward a fixed amount with each swing.</li> <li>In electronic clocks this is an <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electronic_oscillator" title="Electronic oscillator">electronic oscillator circuit</a> that gives the vibrating quartz crystal or tuning fork tiny 'pushes', and generates a series of electrical pulses, one for each vibration of the crystal, which is called the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_signal" title="Clock signal">clock signal</a>.</li> <li>In <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">atomic clocks</a> the controller is an evacuated <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Microwave" title="Microwave">microwave</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cavity_resonator" title="Cavity resonator" class="mw-redirect">cavity</a> attached to a microwave <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electronic_oscillator" title="Electronic oscillator">oscillator</a> controlled by a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Microprocessor" title="Microprocessor">microprocessor</a>. A thin gas of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cesium" title="Cesium" class="mw-redirect">cesium</a> atoms is released into the cavity where they are exposed to <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Microwaves" title="Microwaves" class="mw-redirect">microwaves</a>. A laser measures how many atoms have absorbed the microwaves, and an electronic <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Feedback" title="Feedback">feedback</a> control system called a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Phase-locked_loop" title="Phase-locked loop">phase-locked loop</a> tunes the microwave oscillator until it is at the exact frequency that causes the atoms to vibrate and absorb the microwaves. Then the microwave signal is divided by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_counter" title="Digital counter" class="mw-redirect">digital counters</a> to become the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_signal" title="Clock signal">clock signal</a>.<sup id="cite_ref-52" class="reference"><a href="#cite_note-52"><span>[</span>52<span>]</span></a></sup></li> </ul> <p>In mechanical clocks, the low <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Q_factor" title="Q factor">Q</a> of the balance wheel or pendulum oscillator made them very sensitive to the disturbing effect of the impulses of the escapement, so the escapement had a great effect on the accuracy of the clock, and many escapement designs were tried. The higher Q of resonators in electronic clocks makes them relatively insensitive to the disturbing effects of the drive power, so the driving oscillator circuit is a much less critical component.<sup id="cite_ref-Marrison_4-3" class="reference"><a href="#cite_note-Marrison-4"><span>[</span>4<span>]</span></a></sup></p> <h3><span class="mw-headline" id="Counter_chain">Counter chain</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=19" title="Edit section: Counter chain">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>This counts the pulses and adds them up to get traditional time units of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Second" title="Second">seconds</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Minute" title="Minute">minutes</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hour" title="Hour">hours</a>, etc. It usually has a provision for <i>setting</i> the clock by manually entering the correct time into the counter.</p> <ul> <li>In mechanical clocks this is done mechanically by a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gear_train" title="Gear train">gear train</a>, known as the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wheel_train_(horology)" title="Wheel train (horology)" class="mw-redirect">wheel train</a>. The gear train also has a second function; to transmit mechanical power from the power source to run the oscillator. There is a friction coupling called the 'cannon pinion' between the gears driving the hands and the rest of the clock, allowing the hands to be turned to set the time.<sup id="cite_ref-53" class="reference"><a href="#cite_note-53"><span>[</span>53<span>]</span></a></sup></li> <li>In digital clocks a series of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Integrated_circuit" title="Integrated circuit">integrated circuit</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Counter_(digital)" title="Counter (digital)">counters</a> or dividers add the pulses up <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_data" title="Digital data">digitally</a>, using <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Binary_numeral_system" title="Binary numeral system" class="mw-redirect">binary</a> logic. Often pushbuttons on the case allow the hour and minute counters to be incremented and decremented to set the time.</li> </ul> <h3><span class="mw-headline" id="Indicator">Indicator</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=20" title="Edit section: Indicator">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"> <div id="mwe_player_0" class="PopUpMediaTransform" style="width:220px;" videopayload="<div class="mediaContainer" style="position:relative;display:block;width:320px"><video id="mwe_player_1" style="width:320px;height:240px" poster="//upload.wikimedia.org/wikipedia/en/thumb/a/a1/Cuckoo_strikes_the_8th_hour.ogv/320px--Cuckoo_strikes_the_8th_hour.ogv.jpg" controls="" preload="none" autoplay="" class="kskin" data-durationhint="35.291666666667" data-startoffset="0" data-mwtitle="Cuckoo_strikes_the_8th_hour.ogv" data-mwprovider="local"><source src="//upload.wikimedia.org/wikipedia/en/transcoded/a/a1/Cuckoo_strikes_the_8th_hour.ogv/Cuckoo_strikes_the_8th_hour.ogv.360p.webm" type="video/webm; codecs=&quot;vp8, vorbis&quot;" transcodekey="360p.webm" data-title="Web streamable WebM (360P)" data-shorttitle="WebM 360P" data-width="320" data-height="240" data-bandwidth="561040" data-framerate="24" /><source src="//upload.wikimedia.org/wikipedia/en/a/a1/Cuckoo_strikes_the_8th_hour.ogv" type="video/ogg; codecs=&quot;theora, vorbis&quot;" data-title="Original Ogg file, 320 × 240 (612 kbps)" data-shorttitle="Ogg source" data-width="320" data-height="240" data-bandwidth="612187" data-framerate="24" /><source src="//upload.wikimedia.org/wikipedia/en/transcoded/a/a1/Cuckoo_strikes_the_8th_hour.ogv/Cuckoo_strikes_the_8th_hour.ogv.160p.ogv" type="video/ogg; codecs=&quot;theora, vorbis&quot;" transcodekey="160p.ogv" data-title="Low bandwidth Ogg video (160P)" data-shorttitle="Ogg 160P" data-width="214" data-height="160" data-bandwidth="191296" data-framerate="15" />Sorry, your browser either has JavaScript disabled or does not have any supported player.<br /> You can <a href="//upload.wikimedia.org/wikipedia/en/a/a1/Cuckoo_strikes_the_8th_hour.ogv">download the clip</a> or <a href="https://www.mediawiki.org/wiki/Special:MyLanguage/Extension:TimedMediaHandler/Client_download">download a player</a> to play the clip in your browser.</video></div>"><img alt="File:Cuckoo strikes the 8th hour.ogv" style="width:220px;height:165px" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/en/thumb/a/a1/Cuckoo_strikes_the_8th_hour.ogv/220px--Cuckoo_strikes_the_8th_hour.ogv.jpg"/><a href="//web.archive.org/web/20150320193459/https://upload.wikimedia.org/wikipedia/en/a/a1/Cuckoo_strikes_the_8th_hour.ogv" title="Play media" target="new"><span class="play-btn-large"><span class="mw-tmh-playtext">Play media</span></span></a></div> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Cuckoo_strikes_the_8th_hour.ogv" class="internal" title="Enlarge"></a></div> A <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cuckoo_clock" title="Cuckoo clock">Cuckoo clock</a> with mechanical <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Automaton" title="Automaton">automaton</a> and sound producer striking on the 8th hour on the analog dial.</div> </div> </div> <p>This displays the count of seconds, minutes, hours, etc. in a human readable form.</p> <ul> <li>The earliest mechanical clocks in the 13th century didn't have a visual indicator and signalled the time <a href="//web.archive.org/web/20150320193459/https://en.wiktionary.org/wiki/audible" class="extiw" title="wikt:audible">audibly</a> by striking <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Bell_(instrument)" title="Bell (instrument)">bells</a>. Many clocks to this day are <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Striking_clock" title="Striking clock">striking clocks</a> which strike the hour.</li> <li>Analog clocks display time with an analog <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_face" title="Clock face">clock face</a>, which consists of a round dial with the numbers 1 through 12, the hours in the day, around the outside. The hours are indicated with an <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hour_hand" title="Hour hand" class="mw-redirect">hour hand</a>, which makes two revolutions in a day, while the minutes are indicated by a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_face" title="Clock face">minute hand</a>, which makes one revolution per hour. In mechanical clocks a gear train drives the hands; in electronic clocks the circuit produces pulses every second which drive a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Stepper_motor" title="Stepper motor">stepper motor</a> and gear train, which move the hands.</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_clock" title="Digital clock">Digital clocks</a> display the time in periodically changing <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Numerical_digit" title="Numerical digit">digits</a> on a digital <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Display_device" title="Display device">display</a>. A common misconception is that a digital clock is more accurate than an analog wall clock, but the indicator type is separate and apart from the accuracy of the timing source.</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Talking_clock" title="Talking clock">Talking clocks</a> and the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Speaking_clock" title="Speaking clock">speaking clock</a> services provided by telephone companies speak the time audibly, using either recorded or digitally <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Voice_synthesis" title="Voice synthesis" class="mw-redirect">synthesized voices</a>.</li> </ul> <h2><span class="mw-headline" id="Types">Types</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=21" title="Edit section: Types">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <p>Clocks can be classified by the type of time display, as well as by the method of timekeeping.</p> <h3><span class="mw-headline" id="Time_display_methods">Time display methods</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=22" title="Edit section: Time display methods">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <h4><span class="mw-headline" id="Analog_clocks">Analog clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=23" title="Edit section: Analog clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h4> <div class="hatnote boilerplate seealso">See also: <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_face" title="Clock face">Clock face</a></div> <div class="thumb tright"> <div class="thumbinner" style="width:302px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Picadillycircuslinearclock.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Picadillycircuslinearclock.jpg/300px-Picadillycircuslinearclock.jpg" width="300" height="201" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Picadillycircuslinearclock.jpg/450px-Picadillycircuslinearclock.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Picadillycircuslinearclock.jpg/600px-Picadillycircuslinearclock.jpg 2x" data-file-width="896" data-file-height="600"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Picadillycircuslinearclock.jpg" class="internal" title="Enlarge"></a></div> A linear clock at <a href="/web/20150320193459/https://en.wikipedia.org/wiki/London" title="London">London</a>'s <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Piccadilly_Circus_tube_station" title="Piccadilly Circus tube station">Piccadilly Circus tube station</a>. The 24 hour band moves across the static map, keeping pace with the apparent movement of the sun above ground, and a pointer fixed on London points to the current time</div> </div> </div> <p>Analog clocks usually indicate time using angles. The most common <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_face" title="Clock face">clock face</a> uses a fixed numbered dial or dials and moving hand or hands. It usually has a circular scale of 12 <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hour" title="Hour">hours</a>, which can also serve as a scale of 60 <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Minute" title="Minute">minutes</a>, and 60 <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Seconds" title="Seconds" class="mw-redirect">seconds</a> if the clock has a second hand. Many other styles and designs have been used throughout the years, including dials divided into 6, 8, 10, and 24 hours. The only other widely used clock face today is the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/24_hour_analog_dial" title="24 hour analog dial" class="mw-redirect">24 hour analog dial</a>, because of the use of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/24_hour_time" title="24 hour time" class="mw-redirect">24 hour time</a> in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Military" title="Military">military</a> organizations and timetables. The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/10-hour_clock" title="10-hour clock" class="mw-redirect">10-hour clock</a> was briefly popular during the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/French_Revolution" title="French Revolution">French Revolution</a>, when the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Metric_system" title="Metric system">metric system</a> was applied to time measurement, and an Italian 6 hour clock was developed in the 18th century, presumably to save power (a clock or watch striking 24 times uses more power).</p> <p>Another type of analog clock is the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sundial" title="Sundial">sundial</a>, which tracks the sun continuously, registering the time by the shadow position of its <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gnomon" title="Gnomon">gnomon</a>. Because the sun does not adjust to daylight savings times, users must add an hour during that time. Corrections must also be made for the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Equation_of_time" title="Equation of time">equation of time</a>, and for the difference between the longitudes of the sundial and of the central meridian of the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_zone" title="Time zone">time zone</a> that is being used (i.e. 15 degrees east of the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Prime_meridian" title="Prime meridian">prime meridian</a> for each hour that the time zone is ahead of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/GMT" title="GMT" class="mw-redirect">GMT</a>). Sundials use some or part of the 24 hour analog dial. There also exist clocks which use a digital display despite having an analog mechanism—these are commonly referred to as <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Flip_clock" title="Flip clock">flip clocks</a>.</p> <p>Alternative systems have been proposed. For example, the Twelv clock indicates the current hour using one of twelve colors, and indicates the minute by showing a proportion of a circular disk, similar to a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lunar_phase" title="Lunar phase">moon phase</a>.<sup id="cite_ref-54" class="reference"><a href="#cite_note-54"><span>[</span>54<span>]</span></a></sup></p> <div style="clear:both;"></div> <h4><span class="mw-headline" id="Digital_clocks">Digital clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=24" title="Edit section: Digital clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h4> <div class="hatnote relarticle mainarticle">Main article: <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_clock" title="Digital clock">Digital clock</a></div> <p>Click on any image to enlarge it.</p> <ul class="gallery mw-gallery-traditional"> <li class="gallerybox" style="width: 215px"> <div style="width: 215px"> <div class="thumb" style="width: 210px;"> <div style="margin:79px auto;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:KanazawaStationClock.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/0/00/KanazawaStationClock.jpg/180px-KanazawaStationClock.jpg" width="180" height="122" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/0/00/KanazawaStationClock.jpg/270px-KanazawaStationClock.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/0/00/KanazawaStationClock.jpg/360px-KanazawaStationClock.jpg 2x" data-file-width="1818" data-file-height="1228"/></a></div> </div> <div class="gallerytext"> <p>Digital clock outside <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Kanazawa_Station" title="Kanazawa Station">Kanazawa Station</a> displaying the time by controlling valves on a fountain</p> </div> </div> </li> <li class="gallerybox" style="width: 215px"> <div style="width: 215px"> <div class="thumb" style="width: 210px;"> <div style="margin:80px auto;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Digital-clock-radio-basic_hf.jpg" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/4/43/Digital-clock-radio-basic_hf.jpg/180px-Digital-clock-radio-basic_hf.jpg" width="180" height="120" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/4/43/Digital-clock-radio-basic_hf.jpg/270px-Digital-clock-radio-basic_hf.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/4/43/Digital-clock-radio-basic_hf.jpg/360px-Digital-clock-radio-basic_hf.jpg 2x" data-file-width="2500" data-file-height="1667"/></a></div> </div> <div class="gallerytext"> <p>Basic digital clock radio</p> </div> </div> </li> <li class="gallerybox" style="width: 215px"> <div style="width: 215px"> <div class="thumb" style="width: 210px;"> <div style="margin:15px auto;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:CyanogenMod_10_homescreen_screenshot.png" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/69/CyanogenMod_10_homescreen_screenshot.png/140px-CyanogenMod_10_homescreen_screenshot.png" width="140" height="250" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/69/CyanogenMod_10_homescreen_screenshot.png/211px-CyanogenMod_10_homescreen_screenshot.png 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/6/69/CyanogenMod_10_homescreen_screenshot.png/281px-CyanogenMod_10_homescreen_screenshot.png 2x" data-file-width="720" data-file-height="1280"/></a></div> </div> <div class="gallerytext"> <p><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mobile_phone" title="Mobile phone">Mobile phone</a> display including two clocks, analog-style (albeit generated by a digital computer) in the middle, and digital-style in the top right corner.</p> </div> </div> </li> <li class="gallerybox" style="width: 215px"> <div style="width: 215px"> <div class="thumb" style="width: 210px;"> <div style="margin:61.5px auto;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Analog_clock_with_digital_display.png" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Analog_clock_with_digital_display.png/180px-Analog_clock_with_digital_display.png" width="180" height="157" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Analog_clock_with_digital_display.png/270px-Analog_clock_with_digital_display.png 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/5/5e/Analog_clock_with_digital_display.png/360px-Analog_clock_with_digital_display.png 2x" data-file-width="500" data-file-height="435"/></a></div> </div> <div class="gallerytext"> <p>Diagram of mechanical digital display, as used in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Flip_clock" title="Flip clock">flip clocks</a></p> </div> </div> </li> </ul> <p>Digital clocks display a numeric representation of time. Two numeric display formats are commonly used on <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_data" title="Digital data">digital</a> clocks:</p> <ul> <li>the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/24-hour_notation" title="24-hour notation" class="mw-redirect">24-hour notation</a> with hours ranging 00–23;</li> <li>the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/12-hour_notation" title="12-hour notation" class="mw-redirect">12-hour notation</a> with AM/PM indicator, with hours indicated as 12AM, followed by 1AM–11AM, followed by 12PM, followed by 1PM–11PM (a notation mostly used in domestic environments).</li> </ul> <p>Most digital clocks use electronic mechanisms and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/LCD" title="LCD" class="mw-redirect">LCD</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/LED" title="LED" class="mw-redirect">LED</a>, or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Vacuum_fluorescent_display" title="Vacuum fluorescent display">VFD</a> displays; many other display technologies are used as well (<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cathode_ray_tube" title="Cathode ray tube">cathode ray tubes</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Nixie_tube" title="Nixie tube">nixie tubes</a>, etc.). After a reset, battery change or power failure, these clocks without a backup <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Battery_(electricity)" title="Battery (electricity)">battery</a> or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Capacitor" title="Capacitor">capacitor</a> either start counting from 12:00, or stay at 12:00, often with blinking digits indicating that the time needs to be set. Some newer clocks will reset themselves based on radio or Internet <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_server" title="Time server">time servers</a> that are tuned to national <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">atomic clocks</a>. Since the advent of digital clocks in the 1960s, the use of analog clocks has declined significantly.</p> <p>Some clocks, called '<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Flip_clock" title="Flip clock">flip clocks</a>', have digital displays that work mechanically. The digits are painted on sheets of material which are mounted like the pages of a book. Once a minute, a page is turned over to reveal the next digit. These displays are usually easier to read in brightly lit conditions than LCDs or LEDs. Also, they do not go back to 12:00 after a power interruption. Flip clocks generally do not have electronic mechanisms. Usually, they are driven by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Alternating_current" title="Alternating current">AC</a>-<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Synchronous_motor" title="Synchronous motor">synchronous motors</a>.</p> <h4><span class="mw-headline" id="Auditory_clocks">Auditory clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=25" title="Edit section: Auditory clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h4> <div class="hatnote relarticle mainarticle">Main article: <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Talking_clock" title="Talking clock">Talking clock</a></div> <p>For convenience, distance, telephony or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Blindness" title="Blindness">blindness</a>, auditory clocks present the time as sounds. The sound is either spoken <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Natural_language" title="Natural language">natural language</a>, (e.g. "The time is twelve thirty-five"), or as auditory codes (e.g. number of sequential bell rings on the hour represents the number of the hour like the bell <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_Tower,_Palace_of_Westminster" title="Clock Tower, Palace of Westminster" class="mw-redirect">Big Ben</a>). Most telecommunication companies also provide a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Speaking_clock" title="Speaking clock">speaking clock</a> service as well.</p> <h4><span class="mw-headline" id="Word_clocks">Word clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=26" title="Edit section: Word clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h4> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Word_clock_wallpaper_with_comic_speech_bubble_style.png" class="image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Word_clock_wallpaper_with_comic_speech_bubble_style.png/220px-Word_clock_wallpaper_with_comic_speech_bubble_style.png" width="220" height="138" class="thumbimage" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Word_clock_wallpaper_with_comic_speech_bubble_style.png/330px-Word_clock_wallpaper_with_comic_speech_bubble_style.png 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Word_clock_wallpaper_with_comic_speech_bubble_style.png/440px-Word_clock_wallpaper_with_comic_speech_bubble_style.png 2x" data-file-width="1280" data-file-height="800"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Word_clock_wallpaper_with_comic_speech_bubble_style.png" class="internal" title="Enlarge"></a></div> Software word clock</div> </div> </div> <p>Word clocks are clocks that display the time visually using sentences. E.g.: "It’s about three o’clock." These clocks can be implemented in hardware or software.</p> <h4><span class="mw-headline" id="Projection_clocks">Projection clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=27" title="Edit section: Projection clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h4> <div class="hatnote relarticle mainarticle">Main article: <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Projection_clock" title="Projection clock">Projection clock</a></div> <p>Some clocks, usually digital ones, include an optical <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Image_projector" title="Image projector" class="mw-redirect">projector</a> that shines a magnified image of the time display onto a screen or onto a surface such as an indoor ceiling or wall. The digits are large enough to be easily read, without using glasses, by persons with moderately imperfect vision, so the clocks are convenient for use in their bedrooms. Usually, the timekeeping circuitry has a battery as a backup source for an uninterrupted power supply to keep the clock on time, while the projection light only works when the unit is connected to an A.C. supply. Completely battery-powered portable versions resembling <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Flashlight" title="Flashlight">flashlights</a> are also available.</p> <h4><span class="mw-headline" id="Tactile_clocks">Tactile clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=28" title="Edit section: Tactile clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h4> <p>Auditory and projection clocks can be used by people who are blind or have limited vision. There are also clocks for the blind that have displays that can be read by using the sense of touch. Some of these are similar to normal analog displays, but are constructed so the hands can be felt without damaging them. Another type is essentially digital, and uses devices that use a code such as <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Braille" title="Braille">Braille</a> to show the digits so that they can be felt with the fingertips.</p> <h4><span class="mw-headline" id="Multi-display_clocks">Multi-display clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=29" title="Edit section: Multi-display clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h4> <p>Some clocks have several displays driven by a single mechanism, and some others have several completely separate mechanisms in a single case. Clocks in public places often have several faces visible from different directions, so that the clock can be read from anywhere in the vicinity. Of course, all the faces show the same time. Other clocks show the current time in several time-zones. Watches that are intended to be carried by travellers often have two displays, one for the local time and the other for the time at home, which is useful for making pre-arranged phone calls. Some <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Equation_clock" title="Equation clock">equation clocks</a> have two displays, one showing <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Local_mean_time" title="Local mean time">mean time</a> and the other <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_time#Apparent_solar_time" title="Solar time">solar time</a>, as would be shown by a sundial. Some clocks have both analog and digital displays. Clocks with Braille displays usually also have conventional digits so they can be read by sighted people.</p> <h2><span class="mw-headline" id="Purposes">Purposes</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=30" title="Edit section: Purposes">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <p>Clocks are in homes, offices and many other places; smaller ones (<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Watch" title="Watch">watches</a>) are carried on the wrist or in a pocket; larger ones are in public places, e.g. a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Railway_station" title="Railway station" class="mw-redirect">railway station</a> or <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Church_(building)" title="Church (building)">church</a>. A small clock is often shown in a corner of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Computer_display" title="Computer display" class="mw-redirect">computer displays</a>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mobile_phone" title="Mobile phone">mobile phones</a> and many <a href="/web/20150320193459/https://en.wikipedia.org/wiki/MP3_player" title="MP3 player" class="mw-redirect">MP3 players</a>.</p> <p>The primary purpose of a clock is to <i>display</i> the time. Clocks may also have the facility to make a loud alert signal at a specified time, typically to waken a sleeper at a preset time; they are referred to as <i>alarm clocks</i>. The alarm may start at a low volume and become louder, or have the facility to be switched off for a few minutes then resume. Alarm clocks with visible indicators are sometimes used to indicate to children too young to read the time that the time for sleep has finished; they are sometimes called <i>training clocks</i>.</p> <p>A clock mechanism may be used to <i>control</i> a device according to time, e.g. a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Central_heating" title="Central heating">central heating</a> system, a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/VCR" title="VCR" class="mw-redirect">VCR</a>, or a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_bomb" title="Time bomb">time bomb</a> (see: <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_counter" title="Digital counter" class="mw-redirect">digital counter</a>). Such mechanisms are usually called <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Timer" title="Timer">timers</a>. Clock mechanisms are also used to drive devices such as <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_tracker#Chronological_tracker" title="Solar tracker">solar trackers</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Telescope_mount#Equatorial_mounts" title="Telescope mount">astronomical telescopes</a>, which have to turn at accurately controlled speeds to counteract the rotation of the Earth.</p> <p>Most <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_computer" title="Digital computer" class="mw-redirect">digital computers</a> depend on an internal signal at constant frequency to synchronize processing; this is referred to as a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_signal" title="Clock signal">clock signal</a>. (A few research projects are developing CPUs based on <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Asynchronous_circuit" title="Asynchronous circuit">asynchronous circuits</a>.) Some equipment, including computers, also maintains time and date for use as required; this is referred to as time-of-day clock, and is distinct from the system clock signal, although possibly based on counting its cycles.</p> <h3><span class="mw-headline" id="Time_standards">Time standards</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=31" title="Edit section: Time standards">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <div class="hatnote relarticle mainarticle">Main articles: <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_standard" title="Time standard">Time standard</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">Atomic clock</a></div> <p>For some scientific work timing of the utmost accuracy is essential. It is also necessary to have a standard of the maximum accuracy against which working clocks can be calibrated. An ideal clock would give the time to unlimited accuracy, but this is of course not realisable.</p> <p>Many physical processes, in particular including some <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electronic_transition" title="Electronic transition" class="mw-redirect">transitions</a> between atomic <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Energy_level" title="Energy level">energy levels</a>, occur at exceedingly stable frequency; counting cycles of such a process can give a very accurate and consistent time—clocks which work this way are usually called <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">atomic clocks</a>. Such clocks are typically large, very expensive, require a controlled environment, and are far more accurate than required for most purposes; they are typically used in a <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Metrology#Laboratories" title="Metrology">standards laboratory</a>.</p> <h3><span class="mw-headline" id="Navigation">Navigation</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=32" title="Edit section: Navigation">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>Until advances in the late twentieth century, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Navigation" title="Navigation">navigation</a> depended on the ability to measure <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Latitude" title="Latitude">latitude</a> and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Longitude" title="Longitude">longitude</a>. Latitude can be determined through <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Celestial_navigation" title="Celestial navigation">celestial navigation</a>; the measurement of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Longitude" title="Longitude">longitude</a> requires accurate knowledge of time. This need was a major motivation for the development of accurate mechanical clocks. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/John_Harrison" title="John Harrison">John Harrison</a> created the first highly accurate <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Marine_chronometer" title="Marine chronometer">marine chronometer</a> in the mid-18th century. The <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Noon_gun" title="Noon gun" class="mw-redirect">Noon gun</a> in <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cape_Town" title="Cape Town">Cape Town</a> still fires an accurate signal to allow ships to check their <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Marine_chronometer" title="Marine chronometer">chronometers</a>. Many buildings near major ports used to have (some still do) a large <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_ball" title="Time ball">ball</a> mounted on a tower or mast arranged to drop at a pre-determined time, for the same purpose.</p> <p>While <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Satellite_navigation" title="Satellite navigation">satellite navigation</a> systems such as the <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Global_Positioning_System" title="Global Positioning System">Global Positioning System</a> (GPS) require unprecedentedly accurate knowledge of time, this is supplied by equipment on the satellites; vehicles no longer need timekeeping equipment.</p> <h3><span class="mw-headline" id="Seismology">Seismology</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=33" title="Edit section: Seismology">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <p>In determining the location of an <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Earthquake" title="Earthquake">earthquake</a>, the arrival time of several types of <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Seismic_wave" title="Seismic wave">seismic wave</a> at a minimum of four dispersed observers is dependent upon each observer recording wave <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Arrival_time" title="Arrival time" class="mw-redirect">arrival times</a> according to a common clock.</p> <h2><span class="mw-headline" id="Specific_types_of_clocks">Specific types of clocks</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=34" title="Edit section: Specific types of clocks">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <table> <tr> <td>By mechanism</td> <td>By function</td> <td>By style</td> </tr> <tr> <td style="width:30%;vertical-align:top"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astronomical_clock" title="Astronomical clock">Astronomical clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">Atomic clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Candle_clock" title="Candle clock">Candle clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Congreve_clock" title="Congreve clock">Congreve clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_clock" title="Digital clock">Digital clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Electric_clock" title="Electric clock">Electric clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Analog_clock_with_digital_display" title="Analog clock with digital display" class="mw-redirect">Flip clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hourglass" title="Hourglass">Hourglass</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Incense_clock" title="Incense clock">Incense clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mechanical_watch" title="Mechanical watch">Mechanical watch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Oil-lamp_clock" title="Oil-lamp clock">Oil-lamp clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pendulum_clock" title="Pendulum clock">Pendulum clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pipe_organ_clock" title="Pipe organ clock">Pipe organ clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Projection_clock" title="Projection clock">Projection clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Pulsar_clock" title="Pulsar clock">Pulsar clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Quantum_clock" title="Quantum clock">Quantum clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Quartz_clock" title="Quartz clock">Quartz clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Radio_clock" title="Radio clock">Radio clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Rolling_ball_clock" title="Rolling ball clock">Rolling ball clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Spring_Drive" title="Spring Drive">Spring drive watch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Steam_clock" title="Steam clock">Steam clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sundial" title="Sundial">Sundial</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Torsion_pendulum_clock" title="Torsion pendulum clock">Torsion pendulum clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Water_clock" title="Water clock">Water clock</a></li> </ul> </td> <td style="width:30%;vertical-align:top"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/10-hour_clock" title="10-hour clock" class="mw-redirect">10-hour clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Alarm_clock" title="Alarm clock">Alarm clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Binary_clock" title="Binary clock">Binary clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chiming_clock" title="Chiming clock" class="mw-redirect">Chiming clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronometer_watch" title="Chronometer watch">Chronometer watch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cuckoo_clock" title="Cuckoo clock">Cuckoo clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Equation_clock" title="Equation clock">Equation clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Game_clock" title="Game clock">Game clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Japanese_clock" title="Japanese clock">Japanese clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Master_clock" title="Master clock">Master clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Musical_clock" title="Musical clock">Musical clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Railroad_chronometers" title="Railroad chronometers" class="mw-redirect">Railroad chronometer</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Slave_clock" title="Slave clock">Slave clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Speaking_clock" title="Speaking clock">Speaking clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Stopwatch" title="Stopwatch">Stopwatch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Striking_clock" title="Striking clock">Striking clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Talking_clock" title="Talking clock">Talking clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tide_clock" title="Tide clock">Tide clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_ball" title="Time ball">Time ball</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_clock" title="Time clock">Time clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/World_clock" title="World clock">World clock</a></li> </ul> </td> <td style="width:30%;vertical-align:top"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/American_clock" title="American clock">American clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Automaton_clock" title="Automaton clock">Automaton clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Balloon_clock" title="Balloon clock">Balloon clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Banjo_clock" title="Banjo clock">Banjo clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Bracket_clock" title="Bracket clock">Bracket clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Carriage_clock" title="Carriage clock">Carriage clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cartel_clock" title="Cartel clock">Cartel clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Kit-Cat_Klock" title="Kit-Cat Klock">Cat clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chariot_clock" title="Chariot clock">Chariot clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_tower" title="Clock tower">Clock tower</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cuckoo_clock" title="Cuckoo clock">Cuckoo clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Doll%27s_head_clock" title="Doll's head clock">Doll's head clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Floral_clock" title="Floral clock">Floral clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/French_Empire_mantel_clock" title="French Empire mantel clock">French Empire mantel clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Granddaughter_clock" title="Granddaughter clock" class="mw-redirect">Granddaughter clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Grandfather_clock" title="Grandfather clock" class="mw-redirect">Grandfather clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Grandmother_clock" title="Grandmother clock" class="mw-redirect">Grandmother clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lantern_clock" title="Lantern clock">Lantern clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lighthouse_Clock" title="Lighthouse Clock" class="mw-redirect">Lighthouse clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Longcase_clock" title="Longcase clock">Longcase (Tall-case) clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mantel_clock" title="Mantel clock">Mantel clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Skeleton_clock" title="Skeleton clock">Skeleton clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_tower" title="Clock tower">Tower clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Turret_clock" title="Turret clock">Turret clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Watch" title="Watch">Watch</a></li> </ul> </td> </tr> </table> <h2><span class="mw-headline" id="See_also">See also</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=35" title="Edit section: See also">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <div class="div-col columns column-count column-count-3" style="-moz-column-count: 3; -webkit-column-count: 3; column-count: 3;"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Allan_variance" title="Allan variance">Allan variance</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/American_Watchmakers-Clockmakers_Institute" title="American Watchmakers-Clockmakers Institute">American Watchmakers-Clockmakers Institute</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/BaselWorld" title="BaselWorld">BaselWorld</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Circadian_rhythm" title="Circadian rhythm">Biological clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Castle_clock" title="Castle clock" class="mw-redirect">Castle clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clockarium" title="Clockarium">Clockarium</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lewis_Mumford#The_clock_as_herald_of_the_Industrial_Revolution" title="Lewis Mumford">Clock as herald of the Industrial Revolution</a> (Lewis Mumford)</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_face" title="Clock face">Clock face</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_network" title="Clock network">Clock network</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_of_the_Long_Now" title="Clock of the Long Now">Clock of the Long Now</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_signal" title="Clock signal">Clock signal</a> (digital circuits)</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clockkeeper" title="Clockkeeper">Clockkeeper</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clockmaker" title="Clockmaker">Clockmaker</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Colgate_Clock_(Indiana)" title="Colgate Clock (Indiana)">Colgate Clock (Indiana)</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Colgate_Clock_(New_Jersey)" title="Colgate Clock (New Jersey)" class="mw-redirect">Colgate Clock (New Jersey)</a>, largest clock in USA</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Corpus_Clock" title="Corpus Clock">Corpus Clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cosmo_Clock_21" title="Cosmo Clock 21">Cosmo Clock 21</a>, world's largest clock</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cox%27s_timepiece" title="Cox's timepiece">Cox's timepiece</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cuckooland_Museum" title="Cuckooland Museum">Cuckooland Museum</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Date_and_time_representation_by_country" title="Date and time representation by country">Date and time representation by country</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Debt_clock" title="Debt clock">Debt clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Le_D%C3%A9fenseur_du_Temps" title="Le Défenseur du Temps">Le Défenseur du Temps</a> (automata)</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Department_of_Defense_master_clock" title="Department of Defense master clock">Department of Defense master clock</a> (U.S.)</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Doomsday_Clock" title="Doomsday Clock">Doomsday Clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Earth_clock" title="Earth clock">Earth clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Equation_clock" title="Equation clock">Equation clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Federation_of_the_Swiss_Watch_Industry_FH" title="Federation of the Swiss Watch Industry FH" class="mw-redirect">Federation of the Swiss Watch Industry FH</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Guard_tour_patrol_system" title="Guard tour patrol system">Guard tour patrol system</a> (watchclocks)</li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Iron_Ring_Clock" title="Iron Ring Clock">Iron Ring Clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Jens_Olsen%27s_World_Clock" title="Jens Olsen's World Clock">Jens Olsen's World Clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Jewel_bearing" title="Jewel bearing">Jewel bearing</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/List_of_biggest_clock_faces" title="List of biggest clock faces" class="mw-redirect">List of biggest clock faces</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/List_of_clocks" title="List of clocks">List of clocks</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/List_of_international_common_standards" title="List of international common standards">List of international common standards</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/List_of_world%27s_largest_cuckoo_clocks" title="List of world's largest cuckoo clocks" class="mw-redirect">List of world's largest cuckoo clocks</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Metrology" title="Metrology">Metrology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mora_clock" title="Mora clock">Mora clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/National_Association_of_Watch_and_Clock_Collectors" title="National Association of Watch and Clock Collectors">National Association of Watch and Clock Collectors</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Replica_watch" title="Replica watch" class="mw-redirect">Replica watch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Rubik%27s_Clock" title="Rubik's Clock">Rubik's Clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Star_clock" title="Star clock">Star clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Singing_bird_box" title="Singing bird box">Singing bird box</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/System_time" title="System time">System time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_to_digital_converter" title="Time to digital converter" class="mw-redirect">Time to digital converter</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Timeline_of_time_measurement_technology" title="Timeline of time measurement technology">Timeline of time measurement technology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Timer" title="Timer">Timer</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Watchmaker" title="Watchmaker">Watchmaker</a></li> </ul> </div> <h3><span class="mw-headline" id="Newsgroup">Newsgroup</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=36" title="Edit section: Newsgroup">edit</a><span class="mw-editsection-bracket">]</span></span></h3> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Alt.horology" title="Alt.horology">alt.horology</a></li> </ul> <h2><span class="mw-headline" id="Notes_and_references">Notes and references</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=37" title="Edit section: Notes and references">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <div class="reflist columns references-column-width" style="-moz-column-width: 50em; -webkit-column-width: 50em; column-width: 50em; list-style-type: decimal;"> <ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text">see Baillie et al., p. 307; Palmer, p. 19; Zea & Cheney, p. 172</span></li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><span class="citation web"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://dictionary.cambridge.org/define.asp?key=14263&dict=CALD">"Cambridge Advanced Learner's Dictionary"</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2009-09-16</span></span>. <q>a device for measuring and showing time, which is usually found in or on a building and is not worn by a person</q></span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.btitle=Cambridge+Advanced+Learner%27s+Dictionary&rft.genre=book&rft_id=http%3A%2F%2Fdictionary.cambridge.org%2Fdefine.asp%3Fkey%3D14263%26dict%3DCALD&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-Dohrn-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-Dohrn_3-0">^</a></b></span> <span class="reference-text"><span class="citation book">Dohrn-van Rossum, Gerhard (1996). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=xYhlNoUu-toC&dq=verge+escapement+technology"><i>History of the Hour: Clocks and Modern Temporal Orders</i></a>. Univ. of Chicago Press. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-226-15511-0" title="Special:BookSources/0-226-15511-0">0-226-15511-0</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=Dohrn-van+Rossum%2C+Gerhard&rft.aufirst=Gerhard&rft.aulast=Dohrn-van+Rossum&rft.btitle=History+of+the+Hour%3A+Clocks+and+Modern+Temporal+Orders&rft.date=1996&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DxYhlNoUu-toC%26dq%3Dverge%2Bescapement%2Btechnology&rft.isbn=0-226-15511-0&rft.pub=Univ.+of+Chicago+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span>, p.103-104</span></li> <li id="cite_note-Marrison-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-Marrison_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Marrison_4-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Marrison_4-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Marrison_4-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><span class="citation journal">Marrison, Warren (1948). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://timepieceperfection.com/THE-BELL-SYSTEM.pdf">"The Evolution of the Quartz Crystal Clock"</a>. <i>Bell System Technical Journal</i> <b>27</b>: 510–588. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a rel="nofollow" class="external text" href="//web.archive.org/web/20150320193459/https://dx.doi.org/10.1002%2Fj.1538-7305.1948.tb01343.x">10.1002/j.1538-7305.1948.tb01343.x</a><span class="reference-accessdate">. Retrieved <span class="nowrap">10 November</span> 2014</span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.atitle=The+Evolution+of+the+Quartz+Crystal+Clock&rft.aufirst=Warren&rft.aulast=Marrison&rft.au=Marrison%2C+Warren&rft.date=1948&rft.genre=article&rft_id=http%3A%2F%2Ftimepieceperfection.com%2FTHE-BELL-SYSTEM.pdf&rft_id=info%3Adoi%2F10.1002%2Fj.1538-7305.1948.tb01343.x&rft.jtitle=Bell+System+Technical+Journal&rft.pages=510-588&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.volume=27" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-Cipolla-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Cipolla_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Cipolla_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><span class="citation book">Cipolla, Carlo M. (2004). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=YSf9MVxa2JEC&pg=PA31&dq=verge+escapement+technology"><i>Clocks and Culture, 1300 to 1700</i></a>. W.W. Norton & Co. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-393-32443-5" title="Special:BookSources/0-393-32443-5">0-393-32443-5</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=Cipolla%2C+Carlo+M.&rft.aufirst=Carlo+M.&rft.aulast=Cipolla&rft.btitle=Clocks+and+Culture%2C+1300+to+1700&rft.date=2004&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DYSf9MVxa2JEC%26pg%3DPA31%26dq%3Dverge%2Bescapement%2Btechnology&rft.isbn=0-393-32443-5&rft.pub=W.W.+Norton+%26+Co.&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span>, p.31</span></li> <li id="cite_note-White-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-White_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-White_6-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-White_6-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><span class="citation book">White, Lynn, Jr. (1962). <i>Medieval Technology and Social Change</i>. UK: Oxford Univ. Press. p. 119.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Lynn%2C+Jr.&rft.aulast=White&rft.au=White%2C+Lynn%2C+Jr.&rft.btitle=Medieval+Technology+and+Social+Change&rft.date=1962&rft.genre=book&rft.pages=119&rft.place=UK&rft.pub=Oxford+Univ.+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><span class="citation web"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://sundialsoc.org.uk/discussions/how-do-sundials-work/">"How Sundials Work"</a>. The British Sundial Society<span class="reference-accessdate">. Retrieved <span class="nowrap">10 November</span> 2014</span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.btitle=How+Sundials+Work&rft.genre=book&rft_id=http%3A%2F%2Fsundialsoc.org.uk%2Fdiscussions%2Fhow-do-sundials-work%2F&rft.pub=The+British+Sundial+Society&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><span class="citation web"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://sundials.org/index.php/all-things-sundial/ancient-sundials">"Ancient Sundials"</a>. North American Sundial Society<span class="reference-accessdate">. Retrieved <span class="nowrap">10 November</span> 2014</span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.btitle=Ancient+Sundials&rft.genre=book&rft_id=http%3A%2F%2Fsundials.org%2Findex.php%2Fall-things-sundial%2Fancient-sundials&rft.pub=North+American+Sundial+Society&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-9"><span class="mw-cite-backlink"><b><a href="#cite_ref-9">^</a></b></span> <span class="reference-text"><a href="#CITEREFTurner1984">Turner 1984</a>, p. 1</span></li> <li id="cite_note-10"><span class="mw-cite-backlink"><b><a href="#cite_ref-10">^</a></b></span> <span class="reference-text"><a href="#CITEREFCowan1958">Cowan 1958</a>, p. 58</span></li> <li id="cite_note-11"><span class="mw-cite-backlink"><b><a href="#cite_ref-11">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://www.sailingissues.com/yachting-guide/tower-of-winds-1.html">Tower of the Winds - Athens</a></span></li> <li id="cite_note-12"><span class="mw-cite-backlink"><b><a href="#cite_ref-12">^</a></b></span> <span class="reference-text"><span class="citation book">James, Peter (1995). <i>Ancient Inventions</i>. New York, NY: Ballantine Books. p. 126. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-345-40102-6" title="Special:BookSources/0-345-40102-6">0-345-40102-6</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Peter&rft.au=James%2C+Peter&rft.aulast=James&rft.btitle=Ancient+Inventions&rft.date=1995&rft.genre=book&rft.isbn=0-345-40102-6&rft.pages=126&rft.place=New+York%2C+NY&rft.pub=Ballantine+Books&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-13"><span class="mw-cite-backlink"><b><a href="#cite_ref-13">^</a></b></span> <span class="reference-text"><span class="citation web">William Godwin (1876). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/https://archive.org/details/livesnecromance04godwgoog">"Lives of the Necromancers"</a>. p. 232.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aulast=William+Godwin&rft.au=William+Godwin&rft.btitle=Lives+of+the+Necromancers&rft.date=1876&rft.genre=book&rft_id=https%3A%2F%2Farchive.org%2Fdetails%2Flivesnecromance04godwgoog&rft.pages=232&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-14"><span class="mw-cite-backlink"><b><a href="#cite_ref-14">^</a></b></span> <span class="reference-text"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Ibn_al-Razzaz_Al-Jazari" title="Ibn al-Razzaz Al-Jazari" class="mw-redirect">Ibn al-Razzaz Al-Jazari</a> (ed. 1974), <i>The Book of Knowledge of Ingenious Mechanical Devices</i>. Translated and annotated by <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Donald_Routledge_Hill" title="Donald Routledge Hill" class="mw-redirect">Donald Routledge Hill</a>, Dordrecht/<a href="/web/20150320193459/https://en.wikipedia.org/wiki/D._Reidel" title="D. Reidel">D. Reidel</a>.</span></li> <li id="cite_note-wmsmith1875-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-wmsmith1875_15-0">^</a></b></span> <span class="reference-text"><span class="citation book">Leonhard Schmitz; Smith, William (1875). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Horologium.html"><i>A Dictionary of Greek and Roman Antiquities</i></a>. London: John Murray. pp. 615‑617.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aulast=Leonhard+Schmitz&rft.au=Leonhard+Schmitz&rft.au=Smith%2C+William&rft.btitle=A+Dictionary+of+Greek+and+Roman+Antiquities&rft.date=1875&rft.genre=book&rft_id=http%3A%2F%2Fpenelope.uchicago.edu%2FThayer%2FE%2FRoman%2FTexts%2Fsecondary%2FSMIGRA%2A%2FHorologium.html&rft.pages=615%E2%80%91617&rft.place=London&rft.pub=John+Murray&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-16"><span class="mw-cite-backlink"><b><a href="#cite_ref-16">^</a></b></span> <span class="reference-text">Modern French "horloge" is very close; Spanish "reloj" and Portuguese "relógio" drop the first part of the word.</span></li> <li id="cite_note-17"><span class="mw-cite-backlink"><b><a href="#cite_ref-17">^</a></b></span> <span class="reference-text"><i>Bulletin de la société archéologique de Sens</i>, year 1867, vol. IX, page 390, available at www.archive.org. See also <a href="//web.archive.org/web/20150320193459/https://fr.wikipedia.org/wiki/Discussion:Horloge" class="extiw" title="fr:Discussion:Horloge">fr:Discussion:Horloge</a></span></li> <li id="cite_note-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-18">^</a></b></span> <span class="reference-text"><span class="citation book"><i>The Chronicle of Jocelin of Brakelond, Monk of St. Edmundsbury: A Picture of Monastic and Social Life on the XIIth Century</i>. London: Chatto and Windus. Translated and edited by L. C. Jane. 1910.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.btitle=The+Chronicle+of+Jocelin+of+Brakelond%2C+Monk+of+St.+Edmundsbury%3A+A+Picture+of+Monastic+and+Social+Life+on+the+XIIth+Century&rft.date=1910&rft.genre=book&rft.place=London&rft.pub=Chatto+and+Windus.+Translated+and+edited+by+L.+C.+Jane&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-19"><span class="mw-cite-backlink"><b><a href="#cite_ref-19">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external free" href="https://web.archive.org/web/20150320193459/http://www.guinnessworldrecords.com/records-4000/first-mechanical-clock/">http://www.guinnessworldrecords.com/records-4000/first-mechanical-clock/</a></span></li> <li id="cite_note-20"><span class="mw-cite-backlink"><b><a href="#cite_ref-20">^</a></b></span> <span class="reference-text">History of Song 宋史, Vol. 340</span></li> <li id="cite_note-Leonardo-21"><span class="mw-cite-backlink"><b><a href="#cite_ref-Leonardo_21-0">^</a></b></span> <span class="reference-text"><span class="citation web"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mario_Taddei" title="Mario Taddei">Mario Taddei</a>. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://www.leonardo3.net/leonardo/qma/img/Press_release_Secrets_UK.pdf">"The Book of Secrets is coming to the world after a thousand years: Automata existed already in the eleventh century!"</a>. Leonardo3<span class="reference-accessdate">. Retrieved <span class="nowrap">2010-03-31</span></span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aulast=Mario+Taddei&rft.au=Mario+Taddei&rft.btitle=The+Book+of+Secrets+is+coming+to+the+world+after+a+thousand+years%3A+Automata+existed+already+in+the+eleventh+century%21&rft.genre=book&rft_id=http%3A%2F%2Fwww.leonardo3.net%2Fleonardo%2Fqma%2Fimg%2FPress_release_Secrets_UK.pdf&rft.pub=Leonardo3&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-22"><span class="mw-cite-backlink"><b><a href="#cite_ref-22">^</a></b></span> <span class="reference-text"><span id="harvCategory:Articles_with_inconsistent_citation_formats" class="citation journal"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Donald_Routledge_Hill" title="Donald Routledge Hill" class="mw-redirect">Donald Routledge Hill</a> (1991). "Arabic Mechanical Engineering: Survey of the Historical sources". <i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Arabic_Sciences_and_Philosophy:_A_Historical_Journal" title="Arabic Sciences and Philosophy: A Historical Journal" class="mw-redirect">Arabic Sciences and Philosophy: A Historical Journal</a></i> (<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cambridge_University_Press" title="Cambridge University Press">Cambridge University Press</a>) <b>1</b> (2): 167–186 [173]. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a rel="nofollow" class="external text" href="//web.archive.org/web/20150320193459/https://dx.doi.org/10.1017%2FS0957423900001478">10.1017/S0957423900001478</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.atitle=Arabic+Mechanical+Engineering%3A+Survey+of+the+Historical+sources&rft.au=Donald+Routledge+Hill&rft.aulast=Donald+Routledge+Hill&rft.date=1991&rft.genre=article&rft_id=info%3Adoi%2F10.1017%2FS0957423900001478&rft.issue=2&rft.jtitle=Arabic+Sciences+and+Philosophy%3A+A+Historical+Journal&rft.pages=167-186+173&rft.pub=Cambridge+University+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.volume=1" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-north-23"><span class="mw-cite-backlink">^ <a href="#cite_ref-north_23-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-north_23-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">North, John. God's Clockmaker: Richard of Wallingford and the Invention of Time. London: Hambledon and London (2005).</span></li> <li id="cite_note-king-24"><span class="mw-cite-backlink">^ <a href="#cite_ref-king_24-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-king_24-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-king_24-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text">King, Henry "Geared to the Stars: the evolution of planetariums, orreries, and astronomical clocks", University of Toronto Press, 1978</span></li> <li id="cite_note-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-25">^</a></b></span> <span class="reference-text">Singer, Charles, et al. <i>Oxford History of Technology: volume II, from the Renaissance to the Industrial Revolution</i> (OUP 1957)pg 650-1</span></li> <li id="cite_note-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-26">^</a></b></span> <span class="reference-text"><span class="citation book">Usher, Abbot Payson (1988). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=xuDDqqa8FlwC&pg=PA305"><i>A History of Mechanical Inventions</i></a>. Courier Dover. p. 305. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-486-25593-X" title="Special:BookSources/0-486-25593-X">0-486-25593-X</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Abbot+Payson&rft.aulast=Usher&rft.au=Usher%2C+Abbot+Payson&rft.btitle=A+History+of+Mechanical+Inventions&rft.date=1988&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DxuDDqqa8FlwC%26pg%3DPA305&rft.isbn=0-486-25593-X&rft.pages=305&rft.pub=Courier+Dover&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-Rossum-27"><span class="mw-cite-backlink"><b><a href="#cite_ref-Rossum_27-0">^</a></b></span> <span class="reference-text"><span class="citation book">Dohrn-van Rossum, Gerhar (1997). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=53K32RiEigMC&pg=PA121"><i>History of the Hour: Clocks and Modern Temporal Orders</i></a>. Univ. of Chicago Press. p. 121. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-226-15510-2" title="Special:BookSources/0-226-15510-2">0-226-15510-2</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=Dohrn-van+Rossum%2C+Gerhar&rft.aufirst=Gerhar&rft.aulast=Dohrn-van+Rossum&rft.btitle=History+of+the+Hour%3A+Clocks+and+Modern+Temporal+Orders&rft.date=1997&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3D53K32RiEigMC%26pg%3DPA121&rft.isbn=0-226-15510-2&rft.pages=121&rft.pub=Univ.+of+Chicago+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-28"><span class="mw-cite-backlink"><b><a href="#cite_ref-28">^</a></b></span> <span class="reference-text"><span class="citation book">Milham, Willis I. (1945). <i>Time and Timekeepers</i>. New York: MacMillan. p. 121. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-7808-0008-7" title="Special:BookSources/0-7808-0008-7">0-7808-0008-7</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Willis+I.&rft.aulast=Milham&rft.au=Milham%2C+Willis+I.&rft.btitle=Time+and+Timekeepers&rft.date=1945&rft.genre=book&rft.isbn=0-7808-0008-7&rft.pages=121&rft.place=New+York&rft.pub=MacMillan&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-29"><span class="mw-cite-backlink"><b><a href="#cite_ref-29">^</a></b></span> <span class="reference-text"><span class="citation encyclopaedia"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=Eb0qAAAAMAAJ&dq=Peter+Henlein+mainspring&q=peter+Henlein#search">"Clock"</a>. <i>The New Encyclopaedia Britannica</i> <b>4</b>. Univ. of Chicago. 1974. p. 747. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-85229-290-2" title="Special:BookSources/0-85229-290-2">0-85229-290-2</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.atitle=Clock&rft.btitle=The+New+Encyclopaedia+Britannica&rft.date=1974&rft.genre=bookitem&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DEb0qAAAAMAAJ%26dq%3DPeter%2BHenlein%2Bmainspring%26q%3Dpeter%2BHenlein%23search&rft.isbn=0-85229-290-2&rft.pages=747&rft.pub=Univ.+of+Chicago&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.volume=4" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-30"><span class="mw-cite-backlink"><b><a href="#cite_ref-30">^</a></b></span> <span class="reference-text"><span class="citation book">Anzovin, Steve; Podell, Janet (2000). <i>Famous First Facts: A record of first happenings, discoveries, and inventions in world history</i>. H.W. Wilson. p. 440. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-8242-0958-3" title="Special:BookSources/0-8242-0958-3">0-8242-0958-3</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=Anzovin%2C+Steve&rft.aufirst=Steve&rft.aulast=Anzovin&rft.au=Podell%2C+Janet&rft.btitle=Famous+First+Facts%3A+A+record+of+first+happenings%2C+discoveries%2C+and+inventions+in+world+history&rft.date=2000&rft.genre=book&rft.isbn=0-8242-0958-3&rft.pages=440&rft.pub=H.W.+Wilson&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-haencyc-31"><span class="mw-cite-backlink"><b><a href="#cite_ref-haencyc_31-0">^</a></b></span> <span class="reference-text">p. 529, "Time and timekeeping instruments", <i>History of astronomy: an encyclopedia</i>, John Lankford, Taylor & Francis, 1997, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/081530322X" class="internal mw-magiclink-isbn">ISBN 0-8153-0322-X</a>.</span></li> <li id="cite_note-32"><span class="mw-cite-backlink"><b><a href="#cite_ref-32">^</a></b></span> <span class="reference-text"><span class="citation book">Usher, Abbott Payson (1988). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=xuDDqqa8FlwC&printsec=frontcover&dq=A+history+of+mechanical+inventions,+Abbott+Payson+Usher#v=onepage&q&f=false"><i>A history of mechanical inventions</i></a>. Courier Dover Publications. p. 209. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-486-25593-X" title="Special:BookSources/0-486-25593-X">0-486-25593-X</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Abbott+Payson&rft.aulast=Usher&rft.au=Usher%2C+Abbott+Payson&rft.btitle=A+history+of+mechanical+inventions&rft.date=1988&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DxuDDqqa8FlwC%26printsec%3Dfrontcover%26dq%3DA%2Bhistory%2Bof%2Bmechanical%2Binventions%2C%2BAbbott%2BPayson%2BUsher%23v%3Donepage%26q%26f%3Dfalse&rft.isbn=0-486-25593-X&rft.pages=209&rft.pub=Courier+Dover+Publications&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-33"><span class="mw-cite-backlink"><b><a href="#cite_ref-33">^</a></b></span> <span class="reference-text"><span class="citation book">Lance Day and Ian McNeil, ed. (1996). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=nqAOAAAAQAAJ&lpg=PP1&pg=PA116#v=onepage"><i>Biographical dictionary of the history of technology</i></a>. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Routledge" title="Routledge">Routledge</a> (Routledge Reference). p. 116. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-415-06042-7" title="Special:BookSources/0-415-06042-7">0-415-06042-7</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.btitle=Biographical+dictionary+of+the+history+of+technology&rft.date=1996&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DnqAOAAAAQAAJ%26lpg%3DPP1%26pg%3DPA116%23v%3Donepage&rft.isbn=0-415-06042-7&rft.pages=116&rft.pub=Routledge+%28Routledge+Reference%29&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-34"><span class="mw-cite-backlink"><b><a href="#cite_ref-34">^</a></b></span> <span class="reference-text"><span class="citation journal"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://www.britishmuseum.org/explore/highlights/highlight_objects/pe_mla/t/table_clock_attributed_to_hans.aspx">"Table clock c. 1650 attributed to Hans Buschmann that uses technical inventions by Jost Bürgi"</a>. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/The_British_Museum" title="The British Museum" class="mw-redirect">The British Museum</a><span class="reference-accessdate">. Retrieved <span class="nowrap">2010-04-11</span></span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.btitle=Table+clock+c.+1650+attributed+to+Hans+Buschmann+that+uses+technical+inventions+by+Jost+B%C3%BCrgi&rft.genre=book&rft_id=http%3A%2F%2Fwww.britishmuseum.org%2Fexplore%2Fhighlights%2Fhighlight_objects%2Fpe_mla%2Ft%2Ftable_clock_attributed_to_hans.aspx&rft.pub=The+British+Museum&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-35"><span class="mw-cite-backlink"><b><a href="#cite_ref-35">^</a></b></span> <span class="reference-text"><span class="citation web"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://www.historyworld.net/wrldhis/PlainTextHistories.asp?groupid=2324&HistoryID=ac08&gtrack=pthc">"History of Clocks"</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.btitle=History+of+Clocks&rft.genre=book&rft_id=http%3A%2F%2Fwww.historyworld.net%2Fwrldhis%2FPlainTextHistories.asp%3Fgroupid%3D2324%26HistoryID%3Dac08%26gtrack%3Dpthc&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-36"><span class="mw-cite-backlink"><b><a href="#cite_ref-36">^</a></b></span> <span class="reference-text"><span class="citation web"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://inventors.about.com/library/weekly/aa072801a.htm">"The History of Mechanical Pendulum Clocks and Quartz Clocks"</a>. <i>about.com</i>. 2012<span class="reference-accessdate">. Retrieved <span class="nowrap">16 June</span> 2012</span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.atitle=The+History+of+Mechanical+Pendulum+Clocks+and+Quartz+Clocks&rft.date=2012&rft.genre=article&rft_id=http%3A%2F%2Finventors.about.com%2Flibrary%2Fweekly%2Faa072801a.htm&rft.jtitle=about.com&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-37"><span class="mw-cite-backlink"><b><a href="#cite_ref-37">^</a></b></span> <span class="reference-text"><span class="citation web"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://www.historyworld.net/wrldhis/PlainTextHistories.asp?groupid=2324&HistoryID=ac08&gtrack=pthc">"History Of Clocks"</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.btitle=History+Of+Clocks&rft.genre=book&rft_id=http%3A%2F%2Fwww.historyworld.net%2Fwrldhis%2FPlainTextHistories.asp%3Fgroupid%3D2324%26HistoryID%3Dac08%26gtrack%3Dpthc&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-38"><span class="mw-cite-backlink"><b><a href="#cite_ref-38">^</a></b></span> <span class="reference-text"><i><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/books?id=aB8OAAAAQAAJ&printsec=frontcover">The principles of Mr Harrison's time-keeper</a></i></span></li> <li id="cite_note-Rigden2003-39"><span class="mw-cite-backlink"><b><a href="#cite_ref-Rigden2003_39-0">^</a></b></span> <span class="reference-text"><span class="citation book">John S. Rigden (2003). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/books?id=FhFxn_lUvz0C"><i>Hydrogen: The Essential Element</i></a>. Harvard University Press. p. 185. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/978-0-674-01252-3" title="Special:BookSources/978-0-674-01252-3">978-0-674-01252-3</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=John+S.+Rigden&rft.aulast=John+S.+Rigden&rft.btitle=Hydrogen%3A+The+Essential+Element&rft.date=2003&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DFhFxn_lUvz0C&rft.isbn=978-0-674-01252-3&rft.pages=185&rft.pub=Harvard+University+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-gould-40"><span class="mw-cite-backlink"><b><a href="#cite_ref-gould_40-0">^</a></b></span> <span class="reference-text"><span class="citation book"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Rupert_Gould" title="Rupert Gould">Gould, Rupert T.</a> (1923). <i>The Marine Chronometer. Its History and Development</i>. London: J. D. Potter. p. 66. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-907462-05-7" title="Special:BookSources/0-907462-05-7">0-907462-05-7</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=Gould%2C+Rupert+T.&rft.aulast=Gould%2C+Rupert+T.&rft.btitle=The+Marine+Chronometer.+Its+History+and+Development&rft.date=1923&rft.genre=book&rft.isbn=0-907462-05-7&rft.pages=66&rft.place=London&rft.pub=J.+D.+Potter&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-41"><span class="mw-cite-backlink"><b><a href="#cite_ref-41">^</a></b></span> <span class="reference-text"><span class="citation book">Glasmeier, Amy (2000). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.co.uk/books?id=cVUSauNST8EC&dq=British+Watch+Company+mass+production&source=gbs_navlinks_s"><i>Manufacturing Time: Global Competition in the Watch Industry, 1795-2000</i></a>. Guilford Press<span class="reference-accessdate">. Retrieved <span class="nowrap">2013-02-07</span></span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=Glasmeier%2C+Amy&rft.aulast=Glasmeier%2C+Amy&rft.btitle=Manufacturing+Time%3A+Global+Competition+in+the+Watch+Industry%2C+1795-2000&rft.date=2000&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.co.uk%2Fbooks%3Fid%3DcVUSauNST8EC%26dq%3DBritish%2BWatch%2BCompany%2Bmass%2Bproduction%26source%3Dgbs_navlinks_s&rft.pub=Guilford+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-Roe1916-42"><span class="mw-cite-backlink"><b><a href="#cite_ref-Roe1916_42-0">^</a></b></span> <span class="reference-text"><span id="CITEREFRoe1916" class="citation">Roe, Joseph Wickham (1916), <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/books?id=X-EJAAAAIAAJ&printsec=titlepage"><i>English and American Tool Builders</i></a>, New Haven, Connecticut: Yale University Press, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Library_of_Congress_Control_Number" title="Library of Congress Control Number">LCCN</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://lccn.loc.gov/16011753">16011753</a></span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Joseph+Wickham&rft.aulast=Roe&rft.au=Roe%2C+Joseph+Wickham&rft.btitle=English+and+American+Tool+Builders&rft.date=1916&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3DX-EJAAAAIAAJ%26printsec%3Dtitlepage&rft.lccn=16011753&rft.place=New+Haven%2C+Connecticut&rft.pub=Yale+University+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span>. Reprinted by McGraw-Hill, New York and London, 1926 (<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Library_of_Congress_Control_Number" title="Library of Congress Control Number">LCCN</a> <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://lccn.loc.gov/27024075">27-24075</a>); and by Lindsay Publications, Inc., Bradley, Illinois, (<a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/9780917914737" class="internal mw-magiclink-isbn">ISBN 978-0-917914-73-7</a>).</span></li> <li id="cite_note-43"><span class="mw-cite-backlink"><b><a href="#cite_ref-43">^</a></b></span> <span class="reference-text"><span class="citation book">Thomson, Ross (2009). <i>Structures of Change in the Mechanical Age: Technological Invention in the United States 1790-1865</i>. Baltimore, MD: The Johns Hopkins University Press. p. 34. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/978-0-8018-9141-0" title="Special:BookSources/978-0-8018-9141-0">978-0-8018-9141-0</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Ross&rft.aulast=Thomson&rft.au=Thomson%2C+Ross&rft.btitle=Structures+of+Change+in+the+Mechanical+Age%3A+Technological+Invention+in+the+United+States+1790-1865&rft.date=2009&rft.genre=book&rft.isbn=978-0-8018-9141-0&rft.pages=34&rft.place=Baltimore%2C+MD&rft.pub=The+Johns+Hopkins+University+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-Jespersen-44"><span class="mw-cite-backlink"><b><a href="#cite_ref-Jespersen_44-0">^</a></b></span> <span class="reference-text"><span class="citation book">Jespersen, James; Fitz-Randolph, Jane; Robb, John (1999). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=Z7chuo4ebUAC&pg=PA42&dq=clock+resonance+pendulum"><i>From Sundials to Atomic Clocks: Understanding Time and Frequency</i></a>. New York: Courier Dover. p. 39. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-486-40913-9" title="Special:BookSources/0-486-40913-9">0-486-40913-9</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=James&rft.au=Fitz-Randolph%2C+Jane&rft.au=Jespersen%2C+James&rft.aulast=Jespersen&rft.au=Robb%2C+John&rft.btitle=From+Sundials+to+Atomic+Clocks%3A+Understanding+Time+and+Frequency&rft.date=1999&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DZ7chuo4ebUAC%26pg%3DPA42%26dq%3Dclock%2Bresonance%2Bpendulum&rft.isbn=0-486-40913-9&rft.pages=39&rft.place=New+York&rft.pub=Courier+Dover&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-45"><span class="mw-cite-backlink"><b><a href="#cite_ref-45">^</a></b></span> <span class="reference-text"><span class="citation web"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://www.indepthinfo.com/clocks/index.shtml">"How clocks work"</a>. <i>InDepthInfo</i>. W. J. Rayment. 2007<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-06-04</span></span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.atitle=How+clocks+work&rft.date=2007&rft.genre=article&rft_id=http%3A%2F%2Fwww.indepthinfo.com%2Fclocks%2Findex.shtml&rft.jtitle=InDepthInfo&rft.pub=W.+J.+Rayment&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-Milham-46"><span class="mw-cite-backlink"><b><a href="#cite_ref-Milham_46-0">^</a></b></span> <span class="reference-text"><span class="citation book">Milham, Willis I. (1945). <i>Time and Timekeepers</i>. New York: MacMillan. p. 74. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-7808-0008-7" title="Special:BookSources/0-7808-0008-7">0-7808-0008-7</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Willis+I.&rft.aulast=Milham&rft.au=Milham%2C+Willis+I.&rft.btitle=Time+and+Timekeepers&rft.date=1945&rft.genre=book&rft.isbn=0-7808-0008-7&rft.pages=74&rft.place=New+York&rft.pub=MacMillan&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-47"><span class="mw-cite-backlink"><b><a href="#cite_ref-47">^</a></b></span> <span class="reference-text">Milham, 1945, p.85</span></li> <li id="cite_note-48"><span class="mw-cite-backlink"><b><a href="#cite_ref-48">^</a></b></span> <span class="reference-text"><span class="citation web"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://tf.nist.gov/general/enc-q.htm">"Quality factor, Q"</a>. <i>Glossary</i>. Time and Frequency Division, NIST (National Institute of Standards and Technology). 2008<span class="reference-accessdate">. Retrieved <span class="nowrap">2008-06-04</span></span>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.atitle=Quality+factor%2C+Q&rft.date=2008&rft.genre=article&rft_id=http%3A%2F%2Ftf.nist.gov%2Fgeneral%2Fenc-q.htm&rft.jtitle=Glossary&rft.pub=Time+and+Frequency+Division%2C+NIST+%28National+Institute+of+Standards+and+Technology%29&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-49"><span class="mw-cite-backlink"><b><a href="#cite_ref-49">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/books?id=Z7chuo4ebUAC&pg=PA44&sig=iBunChocEtJoeKS5p5IgJ1oyl4U">Jespersen 1999, p.47-50</a></span></li> <li id="cite_note-50"><span class="mw-cite-backlink"><b><a href="#cite_ref-50">^</a></b></span> <span class="reference-text"><span class="citation book">Riehle, Fritz (2004). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/?id=WZ34pQV-DXMC&pg=PA9&dq=Q+linewidth+%22split+the+line%22"><i>Frequency Standards: Basics and Applications</i></a>. Germany: Wiley VCH Verlag & Co. p. 9. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/3-527-40230-6" title="Special:BookSources/3-527-40230-6">3-527-40230-6</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Fritz&rft.aulast=Riehle&rft.au=Riehle%2C+Fritz&rft.btitle=Frequency+Standards%3A+Basics+and+Applications&rft.date=2004&rft.genre=book&rft_id=http%3A%2F%2Fbooks.google.com%2F%3Fid%3DWZ34pQV-DXMC%26pg%3DPA9%26dq%3DQ%2Blinewidth%2B%2522split%2Bthe%2Bline%2522&rft.isbn=3-527-40230-6&rft.pages=9&rft.place=Germany&rft.pub=Wiley+VCH+Verlag+%26+Co.&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-51"><span class="mw-cite-backlink"><b><a href="#cite_ref-51">^</a></b></span> <span class="reference-text">Milham, 1945, p.325-328</span></li> <li id="cite_note-52"><span class="mw-cite-backlink"><b><a href="#cite_ref-52">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://books.google.com/books?id=Z7chuo4ebUAC&pg=PA61&sig=r7PLMbI4rhAgfGkfBS-MCJEBkVs">Jespersen 1999, p.52-62</a></span></li> <li id="cite_note-53"><span class="mw-cite-backlink"><b><a href="#cite_ref-53">^</a></b></span> <span class="reference-text">Milham, 1945, p.113</span></li> <li id="cite_note-54"><span class="mw-cite-backlink"><b><a href="#cite_ref-54">^</a></b></span> <span class="reference-text">•<span><a rel="nofollow" class="external text" href="//web.archive.org/web/20150320193459/https://www.google.com/patents/US7079452">U.S. Patent 7,079,452</a></span><br/> •<span><a rel="nofollow" class="external text" href="//web.archive.org/web/20150320193459/https://www.google.com/patents/US7221624">U.S. Patent 7,221,624</a></span></span></li> </ol> </div> <h2><span class="mw-headline" id="Bibliography">Bibliography</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=38" title="Edit section: Bibliography">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <ul> <li>Baillie, G.H., O. Clutton, & C.A. Ilbert. <i>Britten’s Old Clocks and Watches and Their Makers</i> (7th ed.). Bonanza Books (1956).</li> <li>Bolter, David J. <i>Turing's Man: Western Culture in the Computer Age</i>. The University of North Carolina Press, Chapel Hill, N.C. (1984). <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0807841080" class="internal mw-magiclink-isbn">ISBN 0-8078-4108-0</a> pbk. Very good, readable summary of the role of "the clock" in its setting the direction of philosophic movement for the "Western World". Cf. picture on p. 25 showing the <i>verge</i> and <i>foliot</i>. Bolton derived the picture from Macey, p. 20.</li> <li><span class="citation book">Bruton, Eric (1982). The History of Clocks and Watches. New York: Crescent Books Distributed by Crown. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/978-0-517-37744-4" title="Special:BookSources/978-0-517-37744-4">978-0-517-37744-4</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=Bruton%2C+Eric&rft.aufirst=Eric&rft.aulast=Bruton&rft.btitle=The+History+of+Clocks+and+Watches&rft.date=1982&rft.genre=book&rft.isbn=978-0-517-37744-4&rft.place=New+York&rft.pub=Crescent+Books+Distributed+by+Crown&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></li> <li><span class="citation book">Dohrn-van Rossum, Gerhard (1996). <i>History of the Hour: Clocks and Modern Temporal Orders</i>. Trans. Thomas Dunlap. Chicago: The University of Chicago Press. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-226-15510-2" title="Special:BookSources/0-226-15510-2">0-226-15510-2</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.au=Dohrn-van+Rossum%2C+Gerhard&rft.aufirst=Gerhard&rft.aulast=Dohrn-van+Rossum&rft.btitle=History+of+the+Hour%3A+Clocks+and+Modern+Temporal+Orders&rft.date=1996&rft.genre=book&rft.isbn=0-226-15510-2&rft.place=Chicago&rft.pub=The+University+of+Chicago+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></li> <li>Edey, Winthrop. <i>French Clocks</i>. New York: Walker & Co. (1967).</li> <li>Kak, Subhash, Babylonian and Indian Astronomy: Early Connections. February 17, 2003.</li> <li>Kumar, Narendra "Science in Ancient India" (2004). <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/8126120568" class="internal mw-magiclink-isbn">ISBN 81-261-2056-8</a>.</li> <li>Landes, David S. <i>Revolution in Time: Clocks and the Making of the Modern World</i>. Cambridge: Harvard University Press (1983).</li> <li>Landes, David S. <i>Clocks & the Wealth of Nations</i>, <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Daedalus_(journal)" title="Daedalus (journal)">Daedalus Journal</a>, Spring 2003.</li> <li>Lloyd, Alan H. “Mechanical Timekeepers”, <i>A History of Technology,</i> Vol. III. Edited by Charles Joseph Singer et al. Oxford: Clarendon Press (1957), pp. 648–675.</li> <li>Macey, Samuel L., <i>Clocks and the Cosmos: Time in Western Life and Thought</i>, Archon Books, Hamden, Conn. (1980).</li> <li><span class="citation book"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Joseph_Needham" title="Joseph Needham">Needham, Joseph</a> (2000) [1965]. <i>Science & Civilisation in China, Vol. 4, Part 2: Mechanical Engineering</i>. Cambridge: Cambridge University Press. <a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:BookSources/0-521-05803-1" title="Special:BookSources/0-521-05803-1">0-521-05803-1</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AClock&rft.aufirst=Joseph&rft.aulast=Needham&rft.au=Needham%2C+Joseph&rft.btitle=Science+%26+Civilisation+in+China%2C+Vol.+4%2C+Part+2%3A+Mechanical+Engineering&rft.date=2000&rft.genre=book&rft.isbn=0-521-05803-1&rft.place=Cambridge&rft.pub=Cambridge+University+Press&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></li> <li>North, John. <i>God's Clockmaker: Richard of Wallingford and the Invention of Time</i>. London: Hambledon and London (2005).</li> <li>Palmer, Brooks. <i>The Book of American Clocks</i>, The Macmillan Co. (1979).</li> <li>Robinson, Tom. <i>The Longcase Clock</i>. Suffolk, England: Antique Collector’s Club (1981).</li> <li>Smith, Alan. <i>The International Dictionary of Clocks</i>. London: Chancellor Press (1996).</li> <li>Tardy. <i>French Clocks the World Over</i>. Part I and II. Translated with the assistance of Alexander Ballantyne. Paris: Tardy (1981).</li> <li>Yoder, Joella Gerstmeyer. <i>Unrolling Time: Christiaan Huygens and the Mathematization of Nature</i>. New York: Cambridge University Press (1988).</li> <li>Zea, Philip, & Robert Cheney. <i>Clock Making in New England: 1725–1825</i>. Old Sturbridge Village (1992).</li> </ul> <h2><span class="mw-headline" id="External_links">External links</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit&section=39" title="Edit section: External links">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <table class="mbox-small plainlinks" style="border:1px solid #aaa;background-color:#f9f9f9"> <tr> <td class="mbox-image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Wiktionary-logo-en.svg/37px-Wiktionary-logo-en.svg.png" width="37" height="40" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Wiktionary-logo-en.svg/55px-Wiktionary-logo-en.svg.png 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/f/f8/Wiktionary-logo-en.svg/73px-Wiktionary-logo-en.svg.png 2x" data-file-width="1000" data-file-height="1089"/></td> <td class="mbox-text plainlist">Look up <i><b><a href="//web.archive.org/web/20150320193459/https://en.wiktionary.org/wiki/Special:Search/clock" class="extiw" title="wiktionary:Special:Search/clock">clock</a></b></i> in Wiktionary, the free dictionary.</td> </tr> </table> <table class="mbox-small plainlinks" style="border:1px solid #aaa;background-color:#f9f9f9"> <tr> <td class="mbox-image"><img alt="" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png" width="30" height="40" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/45px-Commons-logo.svg.png 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/59px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376"/></td> <td class="mbox-text plainlist">Wikimedia Commons has media related to <i><b><a href="//web.archive.org/web/20150320193459/https://commons.wikimedia.org/wiki/Category:Clocks" class="extiw" title="commons:Category:Clocks">Clocks</a></b></i>.</td> </tr> </table> <ul> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://www.nawcc.org/">National Association of Watch & Clock Collectors Museum</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150320193459/http://www.ieee-uffc.org/main/history.asp?file=marrison">Article, by a key figure in the development of quartz crystal clocks, on the history of timekeeping up to the late 1940s from <i>The Bell System Technical Journal, Vol. XXVII, pp. 510-588, 1948</i></a></li> </ul> <table class="navbox" style="border-spacing:0"> <tr> <td style="padding:2px"> <table class="nowraplinks hlist collapsible collapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"> <tr> <th scope="col" class="navbox-title" colspan="3" style="background:#ee9;"> <div class="plainlinks hlist navbar mini"> <ul> <li class="nv-view"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Template:Time_topics" title="Template:Time topics"><span title="View this template" style="background:#ee9;;;background:none transparent;border:none;">v</span></a></li> <li class="nv-talk"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Template_talk:Time_topics" title="Template talk:Time topics"><span title="Discuss this template" style="background:#ee9;;;background:none transparent;border:none;">t</span></a></li> <li class="nv-edit"><a class="external text" href="//web.archive.org/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Template:Time_topics&action=edit"><span title="Edit this template" style="background:#ee9;;;background:none transparent;border:none;">e</span></a></li> </ul> </div> <div style="font-size:110%"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time" title="Time">Time</a></div> </th> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;">Key concepts</th> <td class="navbox-list navbox-odd" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Past" title="Past">Past</a> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/History" title="History">history</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Deep_time" title="Deep time">deep time</a></li> </ul> </li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Present" title="Present">Present</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Future" title="Future">Future</a> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Futures_studies" title="Futures studies">futurology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Far_future" title="Far future">far future</a></li> </ul> </li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Eternity" title="Eternity">Eternity</a> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Arguments_for_eternity" title="Arguments for eternity">arguments for</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Eternal_return" title="Eternal return">Eternal return</a></li> </ul> </li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Immortality" title="Immortality">Immortality</a></li> </ul> </div> </td> <td class="navbox-image" rowspan="17" style="width:0%;padding:0px 0px 0px 2px;padding-left:0.5em;padding-right:0.5em;"> <div><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:Wooden_hourglass_3.jpg" class="image" title="Wooden hourglass"><img alt="Wooden hourglass" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Wooden_hourglass_3.jpg/76px-Wooden_hourglass_3.jpg" width="76" height="154" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Wooden_hourglass_3.jpg/114px-Wooden_hourglass_3.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/7/70/Wooden_hourglass_3.jpg/152px-Wooden_hourglass_3.jpg 2x" data-file-width="967" data-file-height="1959"/></a></div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;">Measurement and<br/> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_standard" title="Time standard">standards</a></th> <td class="navbox-list navbox-even" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"></div> <table class="nowraplinks navbox-subgroup" style="border-spacing:0"> <tr> <th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal;background:#dd9;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronometry" title="Chronometry">Chronometry</a></th> <td class="navbox-list navbox-even" style="text-align:left;border-left-width:2px;border-left-style:solid;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><b><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UTC</a></b></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Universal_Time" title="Universal Time">UT</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Atomic_Time" title="International Atomic Time">TAI</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Unit_of_time" title="Unit of time">Unit of time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Planck_time" title="Planck time">Planck time</a></li> <li><b><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Second" title="Second">Second</a></b></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Minute" title="Minute">Minute</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hour" title="Hour">Hour</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Day" title="Day">Day</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Week" title="Week">Week</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Month" title="Month">Month</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Year" title="Year">Year</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Decade" title="Decade">Decade</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Century" title="Century">Century</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Millennium" title="Millennium">Millennium</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tropical_year" title="Tropical year">Tropical year</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_year" title="Solar year" class="mw-redirect">Solar year</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sidereal_year" title="Sidereal year">Sidereal year</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal;background:#dd9;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/System_of_measurement" title="System of measurement">Measurement<br/> systems</a></th> <td class="navbox-list navbox-odd" style="text-align:left;border-left-width:2px;border-left-style:solid;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_zone" title="Time zone">Time zone</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/24-hour_clock" title="24-hour clock">24-hour clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Daylight_saving_time" title="Daylight saving time">Daylight saving time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_time" title="Solar time">Solar time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sidereal_time" title="Sidereal time">Sidereal time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Metric_time" title="Metric time">Metric time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Decimal_time" title="Decimal time">Decimal time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hexadecimal_time" title="Hexadecimal time">Hexadecimal time</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal;background:#dd9;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Calendar" title="Calendar">Calendars</a></th> <td class="navbox-list navbox-even" style="text-align:left;border-left-width:2px;border-left-style:solid;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gregorian_calendar" title="Gregorian calendar">Gregorian</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Julian_calendar" title="Julian calendar">Julian</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hebrew_calendar" title="Hebrew calendar">Hebrew</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Islamic_calendar" title="Islamic calendar">Islamic</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lunar_calendar" title="Lunar calendar">Lunar</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_Hijri_calendar" title="Solar Hijri calendar">Solar Hijri</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Maya_calendar" title="Maya calendar">Mayan</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Intercalation_(timekeeping)" title="Intercalation (timekeeping)">Intercalation</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Leap_second" title="Leap second">Leap second</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Leap_year" title="Leap year">Leap year</a></li> </ul> </div> </td> </tr> </table> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;"><strong class="selflink">Clocks</strong></th> <td class="navbox-list navbox-odd" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Horology" title="Horology">Horology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/History_of_timekeeping_devices" title="History of timekeeping devices">History of timekeeping devices</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock#Time-measuring_devices" title="Clock">Main types</a> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astrarium" title="Astrarium">astrarium</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">atomic</a> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Quantum_clock" title="Quantum clock">quantum</a></li> </ul> </li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Marine_chronometer" title="Marine chronometer">marine</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sundial" title="Sundial">sundial</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Watch" title="Watch">watch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Water_clock" title="Water clock">water-based</a></li> </ul> </li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;"> <div class="hlist"> <ul style="line-height:1.2em;"> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronology" title="Chronology">Chronology</a></li> <li>History</li> </ul> </div> </th> <td class="navbox-list navbox-even" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astronomical_chronology" title="Astronomical chronology">Astronomical chronology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Big_History" title="Big History">Big History</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Calendar_era" title="Calendar era">Calendar era</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronicle" title="Chronicle">Chronicle</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Deep_time" title="Deep time">Deep time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Periodization" title="Periodization">Periodization</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Regnal_year" title="Regnal year">Regnal year</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Timeline" title="Timeline">Timeline</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;"> <div class="hlist"> <ul style="line-height:1.2em;"> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Time_in_religion" title="Category:Time in religion">Religion</a></li> <li>Mythology</li> </ul> </div> </th> <td class="navbox-list navbox-odd" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Dreamtime" title="Dreamtime">Dreamtime</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/K%C4%81la_(time)" title="Kāla (time)">Kāla</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Kalachakra" title="Kalachakra">Kalachakra</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Prophecy" title="Prophecy">Prophecy</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_and_fate_deities" title="Time and fate deities">Time and fate deities</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wheel_of_time" title="Wheel of time">Wheel of time</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Philosophy_of_space_and_time" title="Philosophy of space and time">Philosophy of time</a></th> <td class="navbox-list navbox-even" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/A-series_and_B-series" title="A-series and B-series">A-series and B-series</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/B-theory_of_time" title="B-theory of time">B-theory of time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Causality" title="Causality">Causality</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Duration_(philosophy)" title="Duration (philosophy)">Duration</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Endurantism" title="Endurantism">Endurantism</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Eternal_return" title="Eternal return">Eternal return</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Eternalism_(philosophy_of_time)" title="Eternalism (philosophy of time)">Eternalism</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Event_(philosophy)" title="Event (philosophy)">Event</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Perdurantism" title="Perdurantism">Perdurantism</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Presentism_(philosophy_of_time)" title="Presentism (philosophy of time)" class="mw-redirect">Presentism</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Temporal_finitism" title="Temporal finitism">Temporal finitism</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Temporal_parts" title="Temporal parts">Temporal parts</a></li> <li><i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/The_Unreality_of_Time" title="The Unreality of Time">The Unreality of Time</a></i></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;">Human experience<br/> and use of time</th> <td class="navbox-list navbox-odd" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Accounting_period" title="Accounting period">Accounting period</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Fiscal_year" title="Fiscal year">Fiscal year</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mental_chronometry" title="Mental chronometry">Mental chronometry</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Procrastination" title="Procrastination">Procrastination</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Punctuality" title="Punctuality">Punctuality</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Temporal_database" title="Temporal database">Temporal database</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Term_(time)" title="Term (time)">Term</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_discipline" title="Time discipline">Time discipline</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_management" title="Time management">Time management</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_perception" title="Time perception">Time perception</a> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Specious_present" title="Specious present">Specious present</a></li> </ul> </li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time-tracking_software" title="Time-tracking software">Time-tracking software</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time-use_research" title="Time-use research">Time-use research</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time-based_currency" title="Time-based currency">Time-based currency (time banking)</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_value_of_money" title="Time value of money">Time value of money</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_clock" title="Time clock">Time clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Timesheet" title="Timesheet">Timesheet</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;">Time in</th> <td class="navbox-list navbox-even" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"></div> <table class="nowraplinks navbox-subgroup" style="border-spacing:0"> <tr> <th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal;background:#dd9;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Geology" title="Geology">Geology</a></th> <td class="navbox-list navbox-even" style="text-align:left;border-left-width:2px;border-left-style:solid;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Geologic_time_scale" title="Geologic time scale">Geological time</a> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Age_(geology)" title="Age (geology)">age</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronozone" title="Chronozone">chron</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Eon_(geology)" title="Eon (geology)" class="mw-redirect">eon</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Epoch_(geology)" title="Epoch (geology)">epoch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Era_(geology)" title="Era (geology)">era</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Period_(geology)" title="Period (geology)">period</a></li> </ul> </li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Geochronology" title="Geochronology">Geochronology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Geological_history_of_Earth" title="Geological history of Earth">Geological history of Earth</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal;background:#dd9;"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_in_physics" title="Time in physics">Physics</a></th> <td class="navbox-list navbox-odd" style="text-align:left;border-left-width:2px;border-left-style:solid;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Absolute_time_and_space" title="Absolute time and space">Absolute time and space</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Arrow_of_time" title="Arrow of time">Arrow of time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronon" title="Chronon">Chronon</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Coordinate_time" title="Coordinate time">Coordinate time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Imaginary_time" title="Imaginary time">Imaginary time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Planck_epoch" title="Planck epoch">Planck epoch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Planck_time" title="Planck time">Planck time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Proper_time" title="Proper time">Proper time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Rate_(mathematics)" title="Rate (mathematics)">Rate</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Spacetime" title="Spacetime">Spacetime</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Theory_of_relativity" title="Theory of relativity">Theory of relativity</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_dilation" title="Time dilation">Time dilation</a> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gravitational_time_dilation" title="Gravitational time dilation">gravitational</a></li> </ul> </li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_domain" title="Time domain">Time domain</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/T-symmetry" title="T-symmetry">T-symmetry</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal;background:#dd9;">other subject<br/> areas</th> <td class="navbox-list navbox-even" style="text-align:left;border-left-width:2px;border-left-style:solid;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronobiology" title="Chronobiology">Chronobiology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Circadian_rhythm" title="Circadian rhythm">Circadian rhythms</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Dating_methodologies_in_archaeology" title="Dating methodologies in archaeology">Dating methodologies in archaeology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_geography" title="Time geography">Time geography</a></li> </ul> </div> </td> </tr> </table> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group" style="background:#ee9;;background:#dd9;">Related topics</th> <td class="navbox-list navbox-odd" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Carpe_diem" title="Carpe diem">Carpe diem</a></i></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock_position" title="Clock position">Clock position</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Space" title="Space">Space</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/System_time" title="System time">System time</a></li> <li><i><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tempus_fugit" title="Tempus fugit">Tempus fugit</a></i></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_capsule" title="Time capsule">Time capsule</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_complexity" title="Time complexity">Time complexity</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_signature" title="Time signature">Time signature</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_travel" title="Time travel">Time travel</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <td class="navbox-abovebelow" colspan="3" style="background:#ee9;"> <div><b><span class="metadata"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/File:MontreGousset001.jpg" class="image"><img alt="Portal icon" src="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/4/45/MontreGousset001.jpg/16px-MontreGousset001.jpg" width="16" height="14" srcset="//web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/4/45/MontreGousset001.jpg/24px-MontreGousset001.jpg 1.5x, //web.archive.org/web/20150320193459im_/https://upload.wikimedia.org/wikipedia/commons/thumb/4/45/MontreGousset001.jpg/32px-MontreGousset001.jpg 2x" data-file-width="800" data-file-height="697"/></a></span> <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Portal:Time" title="Portal:Time">Time portal</a></b></div> </td> </tr> </table> </td> </tr> </table> <table class="navbox" style="border-spacing:0"> <tr> <td style="padding:2px"> <table class="nowraplinks collapsible collapsed navbox-inner" style="border-spacing:0;background:transparent;color:inherit"> <tr> <th scope="col" class="navbox-title" colspan="2"> <div class="plainlinks hlist navbar mini"> <ul> <li class="nv-view"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Template:Time_measurement_and_standards" title="Template:Time measurement and standards"><span title="View this template" style=";;background:none transparent;border:none;">v</span></a></li> <li class="nv-talk"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Template_talk:Time_measurement_and_standards" title="Template talk:Time measurement and standards"><span title="Discuss this template" style=";;background:none transparent;border:none;">t</span></a></li> <li class="nv-edit"><a class="external text" href="//web.archive.org/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Template:Time_measurement_and_standards&action=edit"><span title="Edit this template" style=";;background:none transparent;border:none;">e</span></a></li> </ul> </div> <div style="font-size:110%">Time measurement and <a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_standard" title="Time standard">standards</a></div> </th> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group">Major subjects</th> <td class="navbox-list navbox-odd hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><b><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time" title="Time">Time</a></b></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronometry" title="Chronometry">Chronometry</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Orders_of_magnitude_(time)" title="Orders of magnitude (time)">Orders of magnitude</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Metrology" title="Metrology">Metrology</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group">International standards</th> <td class="navbox-list navbox-even hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><b><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UTC</a></b></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/UTC_offset" title="UTC offset">UTC offset</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Universal_Time" title="Universal Time">UT</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/%CE%94T" title="ΔT">ΔT</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/DUT1" title="DUT1">DUT1</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Earth_Rotation_and_Reference_Systems_Service" title="International Earth Rotation and Reference Systems Service">IERS</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/ISO_31-1" title="ISO 31-1">ISO 31-1</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/ISO_8601" title="ISO 8601">ISO 8601</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Atomic_Time" title="International Atomic Time">TAI</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/24-hour_clock" title="24-hour clock">24-hour clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time" title="Barycentric Coordinate Time">Barycentric Coordinate Time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Civil_time" title="Civil time">Civil time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Daylight_saving_time" title="Daylight saving time">Daylight saving time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Geocentric_Coordinate_Time" title="Geocentric Coordinate Time">Geocentric Coordinate Time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Date_Line" title="International Date Line">International Date Line</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Leap_second" title="Leap second">Leap second</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_time" title="Solar time">Solar time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Terrestrial_Time" title="Terrestrial Time">Terrestrial Time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_zone" title="Time zone">Time zone</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group">Obsolete standards</th> <td class="navbox-list navbox-odd hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Barycentric_Dynamical_Time" title="Barycentric Dynamical Time">Barycentric Dynamical Time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Ephemeris_time" title="Ephemeris time">Ephemeris time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Greenwich_Mean_Time" title="Greenwich Mean Time">Greenwich Mean Time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Prime_meridian" title="Prime meridian">Prime meridian</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_in_physics" title="Time in physics">Time in physics</a></th> <td class="navbox-list navbox-even hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Absolute_time_and_space" title="Absolute time and space">Absolute time and space</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Spacetime" title="Spacetime">Spacetime</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronon" title="Chronon">Chronon</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Continuous_signal" title="Continuous signal">Continuous time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Coordinate_time" title="Coordinate time">Coordinate time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Cosmological_decade" title="Cosmological decade">Cosmological decade</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Discrete_time" title="Discrete time" class="mw-redirect">Discrete time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Planck_epoch" title="Planck epoch">Planck epoch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Planck_time" title="Planck time">Planck time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Proper_time" title="Proper time">Proper time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Theory_of_relativity" title="Theory of relativity">Theory of relativity</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_dilation" title="Time dilation">Time dilation</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gravitational_time_dilation" title="Gravitational time dilation">Gravitational time dilation</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_domain" title="Time domain">Time domain</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/T-symmetry" title="T-symmetry">T-symmetry</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Horology" title="Horology">Horology</a></th> <td class="navbox-list navbox-odd hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><b><strong class="selflink">Clock</strong></b></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astrarium" title="Astrarium">Astrarium</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Atomic_clock" title="Atomic clock">Atomic clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Complication_(horology)" title="Complication (horology)">Complication</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Equation_of_time" title="Equation of time">Equation of time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/History_of_timekeeping_devices" title="History of timekeeping devices">History of timekeeping devices</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hourglass" title="Hourglass">Hourglass</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Marine_chronometer" title="Marine chronometer">Marine chronometer</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Marine_sandglass" title="Marine sandglass">Marine sandglass</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Radio_clock" title="Radio clock">Radio clock</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sundial" title="Sundial">Sundial</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Watch" title="Watch">Watch</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Water_clock" title="Water clock">Water clock</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Calendar" title="Calendar">Calendar</a></th> <td class="navbox-list navbox-even hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astronomical_year_numbering" title="Astronomical year numbering">Astronomical</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Dominical_letter" title="Dominical letter">Dominical letter</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Epact" title="Epact">Epact</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Equinox" title="Equinox">Equinox</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Gregorian_calendar" title="Gregorian calendar">Gregorian</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hebrew_calendar" title="Hebrew calendar">Hebrew</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hindu_calendar" title="Hindu calendar">Hindu</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Intercalation_(timekeeping)" title="Intercalation (timekeeping)">Intercalation</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Islamic_calendar" title="Islamic calendar">Islamic</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Julian_calendar" title="Julian calendar">Julian</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Leap_year" title="Leap year">Leap year</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lunar_calendar" title="Lunar calendar">Lunar</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lunisolar_calendar" title="Lunisolar calendar">Lunisolar</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Seven-day_week" title="Seven-day week">Seven-day week</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solar_calendar" title="Solar calendar">Solar</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Solstice" title="Solstice">Solstice</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tropical_year" title="Tropical year">Tropical year</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Weekday_determination" title="Weekday determination" class="mw-redirect">Weekday determination</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Weekday_names" title="Weekday names" class="mw-redirect">Weekday names</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group">Archaeology and geology</th> <td class="navbox-list navbox-odd hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Dating_methodologies_in_archaeology" title="Dating methodologies in archaeology">Dating methodologies</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Geologic_time_scale" title="Geologic time scale">Geologic time scale</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/International_Commission_on_Stratigraphy" title="International Commission on Stratigraphy">International Commission on Stratigraphy</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Astronomical_chronology" title="Astronomical chronology">Astronomical chronology</a></th> <td class="navbox-list navbox-even hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Galactic_year" title="Galactic year">Galactic year</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Nuclear_time_scale" title="Nuclear time scale" class="mw-redirect">Nuclear time scale</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Precession_(astronomy)" title="Precession (astronomy)" class="mw-redirect">Precession</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Sidereal_time" title="Sidereal time">Sidereal time</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Unit_of_time" title="Unit of time">Units of time</a></th> <td class="navbox-list navbox-odd hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Century" title="Century">Century</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Day" title="Day">Day</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Decade" title="Decade">Decade</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Fortnight" title="Fortnight">Fortnight</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Hour" title="Hour">Hour</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Jiffy_(time)" title="Jiffy (time)">Jiffy</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Lustrum" title="Lustrum">Lustrum</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Millennium" title="Millennium">Millennium</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Minute" title="Minute">Minute</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Moment_(time)" title="Moment (time)">Moment</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Month" title="Month">Month</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Paksha" title="Paksha">Paksha</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Saeculum" title="Saeculum">Saeculum</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Second" title="Second">Second</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Shake_(unit)" title="Shake (unit)">Shake</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Tide_(time)" title="Tide (time)">Tide</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Week" title="Week">Week</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Year" title="Year">Year</a></li> </ul> </div> </td> </tr> <tr style="height:2px"> <td colspan="2"></td> </tr> <tr> <th scope="row" class="navbox-group">Related topics</th> <td class="navbox-list navbox-even hlist" style="text-align:left;border-left-width:2px;border-left-style:solid;width:100%;padding:0px"> <div style="padding:0em 0.25em"> <ul> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Chronology" title="Chronology">Chronology</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Duration_(philosophy)" title="Duration (philosophy)">Duration</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Mental_chronometry" title="Mental chronometry">Mental chronometry</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Metric_time" title="Metric time">Metric time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/System_time" title="System time">System time</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Time_value_of_money" title="Time value of money">Time value of money</a></li> <li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Timekeeper" title="Timekeeper">Timekeeper</a></li> </ul> </div> </td> </tr> </table> </td> </tr> </table>    <noscript><img src="//web.archive.org/web/20150320193459im_/https://en.wikipedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" title="" width="1" height="1" style="border: none; position: absolute;"/></noscript></div> <div class="printfooter"> Retrieved from "<a dir="ltr" href="https://web.archive.org/web/20150320193459/http://en.wikipedia.org/w/index.php?title=Clock&oldid=652709305">http://en.wikipedia.org/w/index.php?title=Clock&oldid=652709305</a>" </div> <div id="catlinks" class="catlinks"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Clocks" title="Category:Clocks">Clocks</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Use_mdy_dates_from_November_2013" title="Category:Use mdy dates from November 2013">Use mdy dates from November 2013</a></li><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:All_articles_with_unsourced_statements" title="Category:All articles with unsourced statements">All articles with unsourced statements</a></li><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Articles_with_unsourced_statements_from_November_2014" title="Category:Articles with unsourced statements from November 2014">Articles with unsourced statements from November 2014</a></li><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Articles_with_unsourced_statements_from_May_2010" title="Category:Articles with unsourced statements from May 2010">Articles with unsourced statements from May 2010</a></li><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Wikipedia_articles_needing_page_number_citations_from_July_2011" title="Category:Wikipedia articles needing page number citations from July 2011">Wikipedia articles needing page number citations from July 2011</a></li><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Articles_with_unsourced_statements_from_October_2007" title="Category:Articles with unsourced statements from October 2007">Articles with unsourced statements from October 2007</a></li><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Wikipedia_articles_needing_clarification_from_November_2014" title="Category:Wikipedia articles needing clarification from November 2014">Wikipedia articles needing clarification from November 2014</a></li><li><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Category:Commons_category_with_local_link_same_as_on_Wikidata" title="Category:Commons category with local link same as on Wikidata">Commons category with local link same as on Wikidata</a></li></ul></div></div> <div class="visualClear"></div> </div> </div> <div id="mw-navigation"> <h2>Navigation menu</h2> <div id="mw-head"> <div id="p-personal" role="navigation" class="" aria-labelledby="p-personal-label"> <h3 id="p-personal-label">Personal tools</h3> <ul> <li id="pt-createaccount"><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Special:UserLogin&returnto=Clock&type=signup" title="You are encouraged to create an account and log in; however, it is not mandatory">Create account</a></li><li id="pt-login"><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Special:UserLogin&returnto=Clock" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o">Log in</a></li> </ul> </div> <div id="left-navigation"> <div id="p-namespaces" role="navigation" class="vectorTabs" aria-labelledby="p-namespaces-label"> <h3 id="p-namespaces-label">Namespaces</h3> <ul> <li id="ca-nstab-main" class="selected"><span><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock" title="View the content page [c]" accesskey="c">Article</a></span></li> <li id="ca-talk"><span><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Talk:Clock" title="Discussion about the content page [t]" accesskey="t">Talk</a></span></li> </ul> </div> <div id="p-variants" role="navigation" class="vectorMenu emptyPortlet" aria-labelledby="p-variants-label"> <h3 id="p-variants-label"><span>Variants</span><a href="#"></a></h3> <div class="menu"> <ul> </ul> </div> </div> </div> <div id="right-navigation"> <div id="p-views" role="navigation" class="vectorTabs" aria-labelledby="p-views-label"> <h3 id="p-views-label">Views</h3> <ul> <li id="ca-view" class="selected"><span><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Clock">Read</a></span></li> <li id="ca-edit"><span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=edit" title="You can edit this page. Please use the preview button before saving [e]" accesskey="e">Edit</a></span></li> <li id="ca-history" class="collapsible"><span><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=history" title="Past versions of this page [h]" accesskey="h">View history</a></span></li> </ul> </div> <div id="p-cactions" role="navigation" class="vectorMenu emptyPortlet" aria-labelledby="p-cactions-label"> <h3 id="p-cactions-label"><span>More</span><a href="#"></a></h3> <div class="menu"> <ul> </ul> </div> </div> <div id="p-search" role="search"> <h3> <label for="searchInput">Search</label> </h3> <form action="/web/20150320193459/https://en.wikipedia.org/w/index.php" id="searchform"> <div id="simpleSearch"> <input type="search" name="search" placeholder="Search" title="Search Wikipedia [f]" accesskey="f" id="searchInput"/><input type="hidden" value="Special:Search" name="title"/><input type="submit" name="fulltext" value="Search" title="Search Wikipedia for this text" id="mw-searchButton" class="searchButton mw-fallbackSearchButton"/><input type="submit" name="go" value="Go" title="Go to a page with this exact name if one exists" id="searchButton" class="searchButton"/> </div> </form> </div> </div> </div> <div id="mw-panel"> <div id="p-logo" role="banner"><a class="mw-wiki-logo" href="/web/20150320193459/https://en.wikipedia.org/wiki/Main_Page" title="Visit the main page"></a></div> <div class="portal" role="navigation" id="p-navigation" aria-labelledby="p-navigation-label"> <h3 id="p-navigation-label">Navigation</h3> <div class="body"> <ul> <li id="n-mainpage-description"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Main_Page" title="Visit the main page [z]" accesskey="z">Main page</a></li> <li id="n-contents"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Portal:Contents" title="Guides to browsing Wikipedia">Contents</a></li> <li id="n-featuredcontent"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Portal:Featured_content" title="Featured content – the best of Wikipedia">Featured content</a></li> <li id="n-currentevents"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Portal:Current_events" title="Find background information on current events">Current events</a></li> <li id="n-randompage"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:Random" title="Load a random article [x]" accesskey="x">Random article</a></li> <li id="n-sitesupport"><a href="https://web.archive.org/web/20150320193459/https://donate.wikimedia.org/wiki/Special:FundraiserRedirector?utm_source=donate&utm_medium=sidebar&utm_campaign=C13_en.wikipedia.org&uselang=en" title="Support us">Donate to Wikipedia</a></li> <li id="n-shoplink"><a href="//web.archive.org/web/20150320193459/https://shop.wikimedia.org/" title="Visit the Wikimedia Shop">Wikipedia store</a></li> </ul> </div> </div> <div class="portal" role="navigation" id="p-interaction" aria-labelledby="p-interaction-label"> <h3 id="p-interaction-label">Interaction</h3> <div class="body"> <ul> <li id="n-help"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia">Help</a></li> <li id="n-aboutsite"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:About" title="Find out about Wikipedia">About Wikipedia</a></li> <li id="n-portal"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Community_portal" title="About the project, what you can do, where to find things">Community portal</a></li> <li id="n-recentchanges"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:RecentChanges" title="A list of recent changes in the wiki [r]" accesskey="r">Recent changes</a></li> <li id="n-contactpage"><a href="//web.archive.org/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact page</a></li> </ul> </div> </div> <div class="portal" role="navigation" id="p-tb" aria-labelledby="p-tb-label"> <h3 id="p-tb-label">Tools</h3> <div class="body"> <ul> <li id="t-whatlinkshere"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:WhatLinksHere/Clock" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j">What links here</a></li> <li id="t-recentchangeslinked"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:RecentChangesLinked/Clock" title="Recent changes in pages linked from this page [k]" accesskey="k">Related changes</a></li> <li id="t-upload"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u">Upload file</a></li> <li id="t-specialpages"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Special:SpecialPages" title="A list of all special pages [q]" accesskey="q">Special pages</a></li> <li id="t-permalink"><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&oldid=652709305" title="Permanent link to this revision of the page">Permanent link</a></li> <li id="t-info"><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&action=info" title="More information about this page">Page information</a></li> <li id="t-wikibase"><a href="//web.archive.org/web/20150320193459/https://www.wikidata.org/wiki/Q376" title="Link to connected data repository item [g]" accesskey="g">Wikidata item</a></li> <li id="t-cite"><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Special:CiteThisPage&page=Clock&id=652709305" title="Information on how to cite this page">Cite this page</a></li> </ul> </div> </div> <div class="portal" role="navigation" id="p-coll-print_export" aria-labelledby="p-coll-print_export-label"> <h3 id="p-coll-print_export-label">Print/export</h3> <div class="body"> <ul> <li id="coll-create_a_book"><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Special:Book&bookcmd=book_creator&referer=Clock">Create a book</a></li> <li id="coll-download-as-rdf2latex"><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Special:Book&bookcmd=render_article&arttitle=Clock&oldid=652709305&writer=rdf2latex">Download as PDF</a></li> <li id="t-print"><a href="/web/20150320193459/https://en.wikipedia.org/w/index.php?title=Clock&printable=yes" title="Printable version of this page [p]" accesskey="p">Printable version</a></li> </ul> </div> </div> <div class="portal" role="navigation" id="p-lang" aria-labelledby="p-lang-label"> <h3 id="p-lang-label">Languages</h3> <div class="body"> <ul> <li class="interlanguage-link interwiki-als"><a href="//web.archive.org/web/20150320193459/https://als.wikipedia.org/wiki/Uhr" title="Uhr – Alemannisch" lang="als" hreflang="als">Alemannisch</a></li> <li class="interlanguage-link interwiki-am"><a href="//web.archive.org/web/20150320193459/https://am.wikipedia.org/wiki/%E1%88%B0%E1%8A%A0%E1%89%B5_(%E1%88%98%E1%88%B3%E1%88%AA%E1%8B%AB)" title="ሰአት (መሳሪያ) – Amharic" lang="am" hreflang="am">አማርኛ</a></li> <li class="interlanguage-link interwiki-ar"><a href="//web.archive.org/web/20150320193459/https://ar.wikipedia.org/wiki/%D8%B3%D8%A7%D8%B9%D8%A9_(%D8%A2%D9%84%D8%A9)" title="ساعة (آلة) – Arabic" lang="ar" hreflang="ar">العربية</a></li> <li class="interlanguage-link interwiki-an"><a href="//web.archive.org/web/20150320193459/https://an.wikipedia.org/wiki/Reloch" title="Reloch – Aragonese" lang="an" hreflang="an">Aragonés</a></li> <li class="interlanguage-link interwiki-az"><a href="//web.archive.org/web/20150320193459/https://az.wikipedia.org/wiki/Saat" title="Saat – Azerbaijani" lang="az" hreflang="az">Azərbaycanca</a></li> <li class="interlanguage-link interwiki-bn"><a href="//web.archive.org/web/20150320193459/https://bn.wikipedia.org/wiki/%E0%A6%98%E0%A6%A1%E0%A6%BC%E0%A6%BF" title="ঘড়ি – Bengali" lang="bn" hreflang="bn">বাংলা</a></li> <li class="interlanguage-link interwiki-ba"><a href="//web.archive.org/web/20150320193459/https://ba.wikipedia.org/wiki/%D0%A1%D3%99%D2%93%D3%99%D1%82_(%D0%BF%D1%80%D0%B8%D0%B1%D0%BE%D1%80)" title="Сәғәт (прибор) – Bashkir" lang="ba" hreflang="ba">Башҡортса</a></li> <li class="interlanguage-link interwiki-be"><a href="//web.archive.org/web/20150320193459/https://be.wikipedia.org/wiki/%D0%93%D0%B0%D0%B4%D0%B7%D1%96%D0%BD%D0%BD%D1%96%D0%BA" title="Гадзіннік – Belarusian" lang="be" hreflang="be">Беларуская</a></li> <li class="interlanguage-link interwiki-be-x-old"><a href="//web.archive.org/web/20150320193459/https://be-x-old.wikipedia.org/wiki/%D0%93%D0%B0%D0%B4%D0%B7%D1%96%D0%BD%D1%8C%D0%BD%D1%96%D0%BA" title="Гадзіньнік – беларуская (тарашкевіца)‎" lang="be-x-old" hreflang="be-x-old">Беларуская (тарашкевіца)‎</a></li> <li class="interlanguage-link interwiki-bg"><a href="//web.archive.org/web/20150320193459/https://bg.wikipedia.org/wiki/%D0%A7%D0%B0%D1%81%D0%BE%D0%B2%D0%BD%D0%B8%D0%BA" title="Часовник – Bulgarian" lang="bg" hreflang="bg">Български</a></li> <li class="interlanguage-link interwiki-bs"><a href="//web.archive.org/web/20150320193459/https://bs.wikipedia.org/wiki/Sat_(instrument)" title="Sat (instrument) – Bosnian" lang="bs" hreflang="bs">Bosanski</a></li> <li class="interlanguage-link interwiki-br"><a href="//web.archive.org/web/20150320193459/https://br.wikipedia.org/wiki/Horolaj" title="Horolaj – Breton" lang="br" hreflang="br">Brezhoneg</a></li> <li class="interlanguage-link interwiki-ca"><a href="//web.archive.org/web/20150320193459/https://ca.wikipedia.org/wiki/Rellotge" title="Rellotge – Catalan" lang="ca" hreflang="ca">Català</a></li> <li class="interlanguage-link interwiki-cv"><a href="//web.archive.org/web/20150320193459/https://cv.wikipedia.org/wiki/%D0%A1%D0%B5%D1%85%D0%B5%D1%82_(%D1%85%D0%B0%D1%82%C4%95%D1%80)" title="Сехет (хатĕр) – Chuvash" lang="cv" hreflang="cv">Чӑвашла</a></li> <li class="interlanguage-link interwiki-cs"><a href="//web.archive.org/web/20150320193459/https://cs.wikipedia.org/wiki/Hodiny" title="Hodiny – Czech" lang="cs" hreflang="cs">Čeština</a></li> <li class="interlanguage-link interwiki-cy"><a href="//web.archive.org/web/20150320193459/https://cy.wikipedia.org/wiki/Cloc" title="Cloc – Welsh" lang="cy" hreflang="cy">Cymraeg</a></li> <li class="interlanguage-link interwiki-da"><a href="//web.archive.org/web/20150320193459/https://da.wikipedia.org/wiki/Ur" title="Ur – Danish" lang="da" hreflang="da">Dansk</a></li> <li class="interlanguage-link interwiki-de"><a href="//web.archive.org/web/20150320193459/https://de.wikipedia.org/wiki/Uhr" title="Uhr – German" lang="de" hreflang="de">Deutsch</a></li> <li class="interlanguage-link interwiki-et"><a href="//web.archive.org/web/20150320193459/https://et.wikipedia.org/wiki/Kell" title="Kell – Estonian" lang="et" hreflang="et">Eesti</a></li> <li class="interlanguage-link interwiki-el"><a href="//web.archive.org/web/20150320193459/https://el.wikipedia.org/wiki/%CE%A1%CE%BF%CE%BB%CF%8C%CE%B9" title="Ρολόι – Greek" lang="el" hreflang="el">Ελληνικά</a></li> <li class="interlanguage-link interwiki-eml"><a href="//web.archive.org/web/20150320193459/https://eml.wikipedia.org/wiki/Arl%C3%B3i" title="Arlói – Emiliano-Romagnolo" lang="eml" hreflang="eml">Emiliàn e rumagnòl</a></li> <li class="interlanguage-link interwiki-es"><a href="//web.archive.org/web/20150320193459/https://es.wikipedia.org/wiki/Reloj" title="Reloj – Spanish" lang="es" hreflang="es">Español</a></li> <li class="interlanguage-link interwiki-eo"><a href="//web.archive.org/web/20150320193459/https://eo.wikipedia.org/wiki/Horlo%C4%9Do" title="Horloĝo – Esperanto" lang="eo" hreflang="eo">Esperanto</a></li> <li class="interlanguage-link interwiki-eu"><a href="//web.archive.org/web/20150320193459/https://eu.wikipedia.org/wiki/Erloju" title="Erloju – Basque" lang="eu" hreflang="eu">Euskara</a></li> <li class="interlanguage-link interwiki-fa"><a href="//web.archive.org/web/20150320193459/https://fa.wikipedia.org/wiki/%D8%B3%D8%A7%D8%B9%D8%AA" title="ساعت – Persian" lang="fa" hreflang="fa">فارسی</a></li> <li class="interlanguage-link interwiki-fr"><a href="//web.archive.org/web/20150320193459/https://fr.wikipedia.org/wiki/Horloge" title="Horloge – French" lang="fr" hreflang="fr">Français</a></li> <li class="interlanguage-link interwiki-ga"><a href="//web.archive.org/web/20150320193459/https://ga.wikipedia.org/wiki/Clog" title="Clog – Irish" lang="ga" hreflang="ga">Gaeilge</a></li> <li class="interlanguage-link interwiki-gv"><a href="//web.archive.org/web/20150320193459/https://gv.wikipedia.org/wiki/Clag_(traa)" title="Clag (traa) – Manx" lang="gv" hreflang="gv">Gaelg</a></li> <li class="interlanguage-link interwiki-gl"><a href="//web.archive.org/web/20150320193459/https://gl.wikipedia.org/wiki/Reloxo" title="Reloxo – Galician" lang="gl" hreflang="gl">Galego</a></li> <li class="interlanguage-link interwiki-gan"><a href="//web.archive.org/web/20150320193459/https://gan.wikipedia.org/wiki/%E9%90%98" title="鐘 – Gan" lang="gan" hreflang="gan">贛語</a></li> <li class="interlanguage-link interwiki-ko"><a href="//web.archive.org/web/20150320193459/https://ko.wikipedia.org/wiki/%EC%8B%9C%EA%B3%84" title="시계 – Korean" lang="ko" hreflang="ko">한국어</a></li> <li class="interlanguage-link interwiki-hr"><a href="//web.archive.org/web/20150320193459/https://hr.wikipedia.org/wiki/Sat_(instrument)" title="Sat (instrument) – Croatian" lang="hr" hreflang="hr">Hrvatski</a></li> <li class="interlanguage-link interwiki-ilo"><a href="//web.archive.org/web/20150320193459/https://ilo.wikipedia.org/wiki/Pagorasan" title="Pagorasan – Iloko" lang="ilo" hreflang="ilo">Ilokano</a></li> <li class="interlanguage-link interwiki-id"><a href="//web.archive.org/web/20150320193459/https://id.wikipedia.org/wiki/Jam_(alat)" title="Jam (alat) – Indonesian" lang="id" hreflang="id">Bahasa Indonesia</a></li> <li class="interlanguage-link interwiki-ia"><a href="//web.archive.org/web/20150320193459/https://ia.wikipedia.org/wiki/Horologio" title="Horologio – Interlingua" lang="ia" hreflang="ia">Interlingua</a></li> <li class="interlanguage-link interwiki-ie"><a href="//web.archive.org/web/20150320193459/https://ie.wikipedia.org/wiki/Horloge" title="Horloge – Interlingue" lang="ie" hreflang="ie">Interlingue</a></li> <li class="interlanguage-link interwiki-is"><a href="//web.archive.org/web/20150320193459/https://is.wikipedia.org/wiki/Klukka" title="Klukka – Icelandic" lang="is" hreflang="is">Íslenska</a></li> <li class="interlanguage-link interwiki-it"><a href="//web.archive.org/web/20150320193459/https://it.wikipedia.org/wiki/Orologio" title="Orologio – Italian" lang="it" hreflang="it">Italiano</a></li> <li class="interlanguage-link interwiki-he"><a href="//web.archive.org/web/20150320193459/https://he.wikipedia.org/wiki/%D7%A9%D7%A2%D7%95%D7%9F" title="שעון – Hebrew" lang="he" hreflang="he">עברית</a></li> <li class="interlanguage-link interwiki-kn"><a href="//web.archive.org/web/20150320193459/https://kn.wikipedia.org/wiki/%E0%B2%97%E0%B2%A1%E0%B2%BF%E0%B2%AF%E0%B2%BE%E0%B2%B0" title="ಗಡಿಯಾರ – Kannada" lang="kn" hreflang="kn">ಕನ್ನಡ</a></li> <li class="interlanguage-link interwiki-ka"><a href="//web.archive.org/web/20150320193459/https://ka.wikipedia.org/wiki/%E1%83%A1%E1%83%90%E1%83%90%E1%83%97%E1%83%98" title="საათი – Georgian" lang="ka" hreflang="ka">ქართული</a></li> <li class="interlanguage-link interwiki-kk"><a href="//web.archive.org/web/20150320193459/https://kk.wikipedia.org/wiki/%D0%A1%D0%B0%D2%93%D0%B0%D1%82" title="Сағат – Kazakh" lang="kk" hreflang="kk">Қазақша</a></li> <li class="interlanguage-link interwiki-sw"><a href="//web.archive.org/web/20150320193459/https://sw.wikipedia.org/wiki/Saa_(ala)" title="Saa (ala) – Swahili" lang="sw" hreflang="sw">Kiswahili</a></li> <li class="interlanguage-link interwiki-ky"><a href="//web.archive.org/web/20150320193459/https://ky.wikipedia.org/wiki/%D0%A1%D0%B0%D0%B0%D1%82" title="Саат – Kyrgyz" lang="ky" hreflang="ky">Кыргызча</a></li> <li class="interlanguage-link interwiki-lo"><a href="//web.archive.org/web/20150320193459/https://lo.wikipedia.org/wiki/%E0%BB%82%E0%BA%A1%E0%BA%87" title="ໂມງ – Lao" lang="lo" hreflang="lo">ລາວ</a></li> <li class="interlanguage-link interwiki-la"><a href="//web.archive.org/web/20150320193459/https://la.wikipedia.org/wiki/Horologium" title="Horologium – Latin" lang="la" hreflang="la">Latina</a></li> <li class="interlanguage-link interwiki-lv"><a href="//web.archive.org/web/20150320193459/https://lv.wikipedia.org/wiki/Pulkstenis" title="Pulkstenis – Latvian" lang="lv" hreflang="lv">Latviešu</a></li> <li class="interlanguage-link interwiki-lb"><a href="//web.archive.org/web/20150320193459/https://lb.wikipedia.org/wiki/Auer" title="Auer – Luxembourgish" lang="lb" hreflang="lb">Lëtzebuergesch</a></li> <li class="interlanguage-link interwiki-lt"><a href="//web.archive.org/web/20150320193459/https://lt.wikipedia.org/wiki/Laikrodis" title="Laikrodis – Lithuanian" lang="lt" hreflang="lt">Lietuvių</a></li> <li class="interlanguage-link interwiki-hu"><a href="//web.archive.org/web/20150320193459/https://hu.wikipedia.org/wiki/%C3%93ra_(eszk%C3%B6z)" title="Óra (eszköz) – Hungarian" lang="hu" hreflang="hu">Magyar</a></li> <li class="interlanguage-link interwiki-mk"><a href="//web.archive.org/web/20150320193459/https://mk.wikipedia.org/wiki/%D0%A7%D0%B0%D1%81%D0%BE%D0%B2%D0%BD%D0%B8%D0%BA" title="Часовник – Macedonian" lang="mk" hreflang="mk">Македонски</a></li> <li class="interlanguage-link interwiki-ml"><a href="//web.archive.org/web/20150320193459/https://ml.wikipedia.org/wiki/%E0%B4%98%E0%B4%9F%E0%B4%BF%E0%B4%95%E0%B4%BE%E0%B4%B0%E0%B4%82" title="ഘടികാരം – Malayalam" lang="ml" hreflang="ml">മലയാളം</a></li> <li class="interlanguage-link interwiki-mr"><a href="//web.archive.org/web/20150320193459/https://mr.wikipedia.org/wiki/%E0%A4%98%E0%A4%A1%E0%A5%8D%E0%A4%AF%E0%A4%BE%E0%A4%B3" title="घड्याळ – Marathi" lang="mr" hreflang="mr">मराठी</a></li> <li class="interlanguage-link interwiki-arz"><a href="//web.archive.org/web/20150320193459/https://arz.wikipedia.org/wiki/%D8%B3%D8%A7%D8%B9%D9%87_(%D8%A2%D9%84%D9%87)" title="ساعه (آله) – Egyptian Spoken Arabic" lang="arz" hreflang="arz">مصرى</a></li> <li class="interlanguage-link interwiki-ms"><a href="//web.archive.org/web/20150320193459/https://ms.wikipedia.org/wiki/Jam_(alat)" title="Jam (alat) – Malay" lang="ms" hreflang="ms">Bahasa Melayu</a></li> <li class="interlanguage-link interwiki-cdo"><a href="//web.archive.org/web/20150320193459/https://cdo.wikipedia.org/wiki/C%E1%B9%B3%CC%86ng" title="Cṳ̆ng – Min Dong Chinese" lang="cdo" hreflang="cdo">Mìng-dĕ̤ng-ngṳ̄</a></li> <li class="interlanguage-link interwiki-mwl"><a href="//web.archive.org/web/20150320193459/https://mwl.wikipedia.org/wiki/Reloijo" title="Reloijo – Mirandese" lang="mwl" hreflang="mwl">Mirandés</a></li> <li class="interlanguage-link interwiki-my"><a href="//web.archive.org/web/20150320193459/https://my.wikipedia.org/wiki/%E1%80%94%E1%80%AC%E1%80%9B%E1%80%AE" title="နာရီ – Burmese" lang="my" hreflang="my">မြန်မာဘာသာ</a></li> <li class="interlanguage-link interwiki-nah"><a href="//web.archive.org/web/20150320193459/https://nah.wikipedia.org/wiki/Tlap%C5%8Dhualtepoztli" title="Tlapōhualtepoztli – Nāhuatl" lang="nah" hreflang="nah">Nāhuatl</a></li> <li class="interlanguage-link interwiki-nl"><a href="//web.archive.org/web/20150320193459/https://nl.wikipedia.org/wiki/Klok_(tijd)" title="Klok (tijd) – Dutch" lang="nl" hreflang="nl">Nederlands</a></li> <li class="interlanguage-link interwiki-new"><a href="//web.archive.org/web/20150320193459/https://new.wikipedia.org/wiki/%E0%A4%88%E0%A4%B2%E0%A4%9A%E0%A4%82" title="ईलचं – Newari" lang="new" hreflang="new">नेपाल भाषा</a></li> <li class="interlanguage-link interwiki-ja"><a href="//web.archive.org/web/20150320193459/https://ja.wikipedia.org/wiki/%E6%99%82%E8%A8%88" title="時計 – Japanese" lang="ja" hreflang="ja">日本語</a></li> <li class="interlanguage-link interwiki-ce"><a href="//web.archive.org/web/20150320193459/https://ce.wikipedia.org/wiki/%D0%A7%D0%B0%D1%81%D1%8B_(%D0%9F%D0%B5%D0%BD%D0%B7%D0%B0%D0%BD_%D0%BE%D0%B1%D0%BB%D0%B0%D1%81%D1%82%D1%8C)" title="Часы (Пензан область) – Chechen" lang="ce" hreflang="ce">Нохчийн</a></li> <li class="interlanguage-link interwiki-no"><a href="//web.archive.org/web/20150320193459/https://no.wikipedia.org/wiki/Klokke_(ur)" title="Klokke (ur) – Norwegian (bokmål)" lang="no" hreflang="no">Norsk bokmål</a></li> <li class="interlanguage-link interwiki-nn"><a href="//web.archive.org/web/20150320193459/https://nn.wikipedia.org/wiki/Klokke" title="Klokke – Norwegian Nynorsk" lang="nn" hreflang="nn">Norsk nynorsk</a></li> <li class="interlanguage-link interwiki-oc"><a href="//web.archive.org/web/20150320193459/https://oc.wikipedia.org/wiki/Rel%C3%B2tge" title="Relòtge – Occitan" lang="oc" hreflang="oc">Occitan</a></li> <li class="interlanguage-link interwiki-uz"><a href="//web.archive.org/web/20150320193459/https://uz.wikipedia.org/wiki/Soat_(asbob)" title="Soat (asbob) – Uzbek" lang="uz" hreflang="uz">Oʻzbekcha/ўзбекча</a></li> <li class="interlanguage-link interwiki-pa"><a href="//web.archive.org/web/20150320193459/https://pa.wikipedia.org/wiki/%E0%A8%98%E0%A9%9C%E0%A9%80" title="ਘੜੀ – Punjabi" lang="pa" hreflang="pa">ਪੰਜਾਬੀ</a></li> <li class="interlanguage-link interwiki-pnb"><a href="//web.archive.org/web/20150320193459/https://pnb.wikipedia.org/wiki/%DA%A9%D8%B9%DA%91%DB%8C" title="کعڑی – Western Punjabi" lang="pnb" hreflang="pnb">پنجابی</a></li> <li class="interlanguage-link interwiki-ps"><a href="//web.archive.org/web/20150320193459/https://ps.wikipedia.org/wiki/%DA%AF%DA%93%D9%8A%D8%A7%D9%84" title="گړيال – Pashto" lang="ps" hreflang="ps">پښتو</a></li> <li class="interlanguage-link interwiki-nds"><a href="//web.archive.org/web/20150320193459/https://nds.wikipedia.org/wiki/Klock_(Tiet)" title="Klock (Tiet) – Low German" lang="nds" hreflang="nds">Plattdüütsch</a></li> <li class="interlanguage-link interwiki-pl"><a href="//web.archive.org/web/20150320193459/https://pl.wikipedia.org/wiki/Zegar" title="Zegar – Polish" lang="pl" hreflang="pl">Polski</a></li> <li class="interlanguage-link interwiki-pt"><a href="//web.archive.org/web/20150320193459/https://pt.wikipedia.org/wiki/Rel%C3%B3gio" title="Relógio – Portuguese" lang="pt" hreflang="pt">Português</a></li> <li class="interlanguage-link interwiki-ro"><a href="//web.archive.org/web/20150320193459/https://ro.wikipedia.org/wiki/Ceas" title="Ceas – Romanian" lang="ro" hreflang="ro">Română</a></li> <li class="interlanguage-link interwiki-qu"><a href="//web.archive.org/web/20150320193459/https://qu.wikipedia.org/wiki/Pacha_tupuq" title="Pacha tupuq – Quechua" lang="qu" hreflang="qu">Runa Simi</a></li> <li class="interlanguage-link interwiki-ru"><a href="//web.archive.org/web/20150320193459/https://ru.wikipedia.org/wiki/%D0%A7%D0%B0%D1%81%D1%8B" title="Часы – Russian" lang="ru" hreflang="ru">Русский</a></li> <li class="interlanguage-link interwiki-sco"><a href="//web.archive.org/web/20150320193459/https://sco.wikipedia.org/wiki/Knock" title="Knock – Scots" lang="sco" hreflang="sco">Scots</a></li> <li class="interlanguage-link interwiki-sq"><a href="//web.archive.org/web/20150320193459/https://sq.wikipedia.org/wiki/Ora" title="Ora – Albanian" lang="sq" hreflang="sq">Shqip</a></li> <li class="interlanguage-link interwiki-scn"><a href="//web.archive.org/web/20150320193459/https://scn.wikipedia.org/wiki/Rul%C3%B2ggiu" title="Rulòggiu – Sicilian" lang="scn" hreflang="scn">Sicilianu</a></li> <li class="interlanguage-link interwiki-simple"><a href="//web.archive.org/web/20150320193459/https://simple.wikipedia.org/wiki/Clock" title="Clock – Simple English" lang="simple" hreflang="simple">Simple English</a></li> <li class="interlanguage-link interwiki-sk"><a href="//web.archive.org/web/20150320193459/https://sk.wikipedia.org/wiki/Hodiny" title="Hodiny – Slovak" lang="sk" hreflang="sk">Slovenčina</a></li> <li class="interlanguage-link interwiki-sl"><a href="//web.archive.org/web/20150320193459/https://sl.wikipedia.org/wiki/Ura_(naprava)" title="Ura (naprava) – Slovenian" lang="sl" hreflang="sl">Slovenščina</a></li> <li class="interlanguage-link interwiki-so"><a href="//web.archive.org/web/20150320193459/https://so.wikipedia.org/wiki/Goorsheegto" title="Goorsheegto – Somali" lang="so" hreflang="so">Soomaaliga</a></li> <li class="interlanguage-link interwiki-ckb"><a href="//web.archive.org/web/20150320193459/https://ckb.wikipedia.org/wiki/%DA%A9%D8%A7%D8%AA%DA%98%D9%85%DB%8E%D8%B1" title="کاتژمێر – Sorani Kurdish" lang="ckb" hreflang="ckb">کوردی</a></li> <li class="interlanguage-link interwiki-sr"><a href="//web.archive.org/web/20150320193459/https://sr.wikipedia.org/wiki/%D0%A7%D0%B0%D1%81%D0%BE%D0%B2%D0%BD%D0%B8%D0%BA" title="Часовник – Serbian" lang="sr" hreflang="sr">Српски / srpski</a></li> <li class="interlanguage-link interwiki-sh"><a href="//web.archive.org/web/20150320193459/https://sh.wikipedia.org/wiki/Sat_(predmet)" title="Sat (predmet) – Serbo-Croatian" lang="sh" hreflang="sh">Srpskohrvatski / српскохрватски</a></li> <li class="interlanguage-link interwiki-su"><a href="//web.archive.org/web/20150320193459/https://su.wikipedia.org/wiki/Jam_Tembok" title="Jam Tembok – Sundanese" lang="su" hreflang="su">Basa Sunda</a></li> <li class="interlanguage-link interwiki-fi"><a href="//web.archive.org/web/20150320193459/https://fi.wikipedia.org/wiki/Kello" title="Kello – Finnish" lang="fi" hreflang="fi">Suomi</a></li> <li class="interlanguage-link interwiki-sv"><a href="//web.archive.org/web/20150320193459/https://sv.wikipedia.org/wiki/Ur" title="Ur – Swedish" lang="sv" hreflang="sv">Svenska</a></li> <li class="interlanguage-link interwiki-ta"><a href="//web.archive.org/web/20150320193459/https://ta.wikipedia.org/wiki/%E0%AE%95%E0%AE%9F%E0%AE%BF%E0%AE%95%E0%AE%BE%E0%AE%B0%E0%AE%AE%E0%AF%8D" title="கடிகாரம் – Tamil" lang="ta" hreflang="ta">தமிழ்</a></li> <li class="interlanguage-link interwiki-th"><a href="//web.archive.org/web/20150320193459/https://th.wikipedia.org/wiki/%E0%B8%99%E0%B8%B2%E0%B8%AC%E0%B8%B4%E0%B8%81%E0%B8%B2" title="นาฬิกา – Thai" lang="th" hreflang="th">ไทย</a></li> <li class="interlanguage-link interwiki-tr"><a href="//web.archive.org/web/20150320193459/https://tr.wikipedia.org/wiki/Saat" title="Saat – Turkish" lang="tr" hreflang="tr">Türkçe</a></li> <li class="interlanguage-link interwiki-uk"><a href="//web.archive.org/web/20150320193459/https://uk.wikipedia.org/wiki/%D0%93%D0%BE%D0%B4%D0%B8%D0%BD%D0%BD%D0%B8%D0%BA" title="Годинник – Ukrainian" lang="uk" hreflang="uk">Українська</a></li> <li class="interlanguage-link interwiki-ur"><a href="//web.archive.org/web/20150320193459/https://ur.wikipedia.org/wiki/%DA%AF%DA%BE%D9%86%D9%B9%D8%A7" title="گھنٹا – Urdu" lang="ur" hreflang="ur">اردو</a></li> <li class="interlanguage-link interwiki-vec"><a href="//web.archive.org/web/20150320193459/https://vec.wikipedia.org/wiki/Rolojo" title="Rolojo – Venetian" lang="vec" hreflang="vec">Vèneto</a></li> <li class="interlanguage-link interwiki-vep"><a href="//web.archive.org/web/20150320193459/https://vep.wikipedia.org/wiki/%C4%8Casud" title="Časud – Veps" lang="vep" hreflang="vep">Vepsän kel’</a></li> <li class="interlanguage-link interwiki-vi"><a href="//web.archive.org/web/20150320193459/https://vi.wikipedia.org/wiki/%C4%90%E1%BB%93ng_h%E1%BB%93" title="Đồng hồ – Vietnamese" lang="vi" hreflang="vi">Tiếng Việt</a></li> <li class="interlanguage-link interwiki-war"><a href="//web.archive.org/web/20150320193459/https://war.wikipedia.org/wiki/Relo" title="Relo – Waray" lang="war" hreflang="war">Winaray</a></li> <li class="interlanguage-link interwiki-yi"><a href="//web.archive.org/web/20150320193459/https://yi.wikipedia.org/wiki/%D7%96%D7%99%D7%99%D7%92%D7%A2%D7%A8" title="זייגער – Yiddish" lang="yi" hreflang="yi">ייִדיש</a></li> <li class="interlanguage-link interwiki-zh-yue"><a href="//web.archive.org/web/20150320193459/https://zh-yue.wikipedia.org/wiki/%E9%90%98" title="鐘 – Cantonese" lang="zh-yue" hreflang="zh-yue">粵語</a></li> <li class="interlanguage-link interwiki-diq"><a href="//web.archive.org/web/20150320193459/https://diq.wikipedia.org/wiki/Saete_(hacet)" title="Saete (hacet) – Zazaki" lang="diq" hreflang="diq">Zazaki</a></li> <li class="interlanguage-link interwiki-zh"><a href="//web.archive.org/web/20150320193459/https://zh.wikipedia.org/wiki/%E6%99%82%E9%90%98" title="時鐘 – Chinese" lang="zh" hreflang="zh">中文</a></li> <li class="uls-p-lang-dummy"><a href="#"></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a action="edit" href="//web.archive.org/web/20150320193459/https://www.wikidata.org/wiki/Q376#sitelinks-wikipedia" text="Edit links" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </div> <div id="footer" role="contentinfo"> <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last modified on 20 March 2015, at 08:42.</li> <li id="footer-info-copyright">Text is available under the <a rel="license" href="//web.archive.org/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Text_of_Creative_Commons_Attribution-ShareAlike_3.0_Unported_License">Creative Commons Attribution-ShareAlike License</a><a rel="license" href="//web.archive.org/web/20150320193459/https://creativecommons.org/licenses/by-sa/3.0/" style="display:none;"></a>; additional terms may apply. By using this site, you agree to the <a href="//web.archive.org/web/20150320193459/https://wikimediafoundation.org/wiki/Terms_of_Use">Terms of Use</a> and <a href="//web.archive.org/web/20150320193459/https://wikimediafoundation.org/wiki/Privacy_policy">Privacy Policy</a>. Wikipedia® is a registered trademark of the <a href="//web.archive.org/web/20150320193459/https://www.wikimediafoundation.org/">Wikimedia Foundation, Inc.</a>, a non-profit organization.</li> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="//web.archive.org/web/20150320193459/https://wikimediafoundation.org/wiki/Privacy_policy" title="wikimedia:Privacy policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:About" title="Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimer"><a href="/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:General_disclaimer" title="Wikipedia:General disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//web.archive.org/web/20150320193459/https://en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-developers"><a href="https://web.archive.org/web/20150320193459/https://www.mediawiki.org/wiki/Special:MyLanguage/How_to_contribute">Developers</a></li> <li id="footer-places-mobileview"><a href="//web.archive.org/web/20150320193459/https://en.m.wikipedia.org/w/index.php?title=Clock&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"> <a href="//web.archive.org/web/20150320193459/https://wikimediafoundation.org/"><img src="//web.archive.org/web/20150320193459im_/https://bits.wikimedia.org/images/wikimedia-button.png" srcset="//web.archive.org/web/20150320193459im_/https://bits.wikimedia.org/images/wikimedia-button-1.5x.png 1.5x, //web.archive.org/web/20150320193459im_/https://bits.wikimedia.org/images/wikimedia-button-2x.png 2x" width="88" height="31" alt="Wikimedia Foundation"/></a> </li> <li id="footer-poweredbyico"> <a href="//web.archive.org/web/20150320193459/https://www.mediawiki.org/"><img src="//web.archive.org/web/20150320193459im_/https://bits.wikimedia.org/static-1.25wmf21/resources/assets/poweredby_mediawiki_88x31.png" alt="Powered by MediaWiki" srcset="//web.archive.org/web/20150320193459im_/https://bits.wikimedia.org/static-1.25wmf21/resources/assets/poweredby_mediawiki_132x47.png 1.5x, //web.archive.org/web/20150320193459im_/https://bits.wikimedia.org/static-1.25wmf21/resources/assets/poweredby_mediawiki_176x62.png 2x" width="88" height="31"/></a> </li> </ul> <div style="clear:both"></div> </div> <script>/*<![CDATA[*/window.jQuery && jQuery.ready();/*]]>*/</script><script>if(window.mw){ mw.loader.state({"ext.globalCssJs.site":"ready","ext.globalCssJs.user":"ready","mw.PopUpMediaTransform":"loading","site":"loading","user":"ready","user.groups":"ready"}); }</script> <script>if(window.mw){ document.write("\u003Cscript src=\"//bits.wikimedia.org/en.wikipedia.org/load.php?debug=false\u0026amp;lang=en\u0026amp;modules=mw.PopUpMediaTransform\u0026amp;only=scripts\u0026amp;skin=vector\u0026amp;*\"\u003E\u003C/script\u003E"); }</script> <script>if(window.mw){ mw.loader.load(["ext.cite","mediawiki.toc","mediawiki.action.view.postEdit","mediawiki.user","mediawiki.hidpi","mediawiki.page.ready","mediawiki.searchSuggest","ext.gadget.teahouse","ext.gadget.ReferenceTooltips","ext.gadget.DRN-wizard","ext.gadget.charinsert","ext.gadget.refToolbar","ext.gadget.switcher","ext.gadget.featured-articles-links","ext.wikiEditor.init","mmv.bootstrap.autostart","ext.imageMetrics.loader","ext.visualEditor.targetLoader","ext.eventLogging.subscriber","ext.wikimediaEvents.statsd","ext.navigationTiming","schema.UniversalLanguageSelector","ext.uls.eventlogger","ext.uls.interlanguage"],null,true); }</script> <script>if(window.mw){ document.write("\u003Cscript src=\"//bits.wikimedia.org/en.wikipedia.org/load.php?debug=false\u0026amp;lang=en\u0026amp;modules=site\u0026amp;only=scripts\u0026amp;skin=vector\u0026amp;*\"\u003E\u003C/script\u003E"); }</script> <script>if(window.mw){ mw.config.set({"wgBackendResponseTime":147,"wgHostname":"mw1041"}); }</script> </body> </html>