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class="vector-toc-list"> <li id="toc-Midnight_00:00_and_24:00" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Midnight_00:00_and_24:00"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.1</span> <span>Midnight 00:00 and 24:00</span> </div> </a> <ul id="toc-Midnight_00:00_and_24:00-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Times_after_24:00" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Times_after_24:00"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.2</span> <span>Times after 24:00</span> </div> </a> <ul id="toc-Times_after_24:00-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Computer_support" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Computer_support"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.3</span> <span>Computer support</span> </div> </a> <ul id="toc-Computer_support-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Military_time" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Military_time"> <div class="vector-toc-text"> <span class="vector-toc-numb">1.4</span> <span>Military time</span> </div> </a> <ul id="toc-Military_time-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-History" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#History"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>History</span> </div> </a> <ul id="toc-History-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Notes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Notes"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Notes</span> </div> </a> <ul id="toc-Notes-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">24-hour clock</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 33 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-33" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">33 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%86%D8%B8%D8%A7%D9%85_24_%D8%B3%D8%A7%D8%B9%D8%A9" title="نظام 24 ساعة – Arabic" lang="ar" hreflang="ar" data-title="نظام 24 ساعة" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A7%A8%E0%A7%AA-%E0%A6%98%E0%A6%A3%E0%A7%8D%E0%A6%9F%E0%A6%BE%E0%A6%B0_%E0%A6%98%E0%A6%A1%E0%A6%BC%E0%A6%BF" title="২৪-ঘণ্টার ঘড়ি – Bangla" lang="bn" hreflang="bn" data-title="২৪-ঘণ্টার ঘড়ি" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-be-x-old mw-list-item"><a href="https://be-tarask.wikipedia.org/wiki/24-%D0%B3%D0%B0%D0%B4%D0%B7%D1%96%D0%BD%D0%BD%D1%8B_%D1%84%D0%B0%D1%80%D0%BC%D0%B0%D1%82_%D1%87%D0%B0%D1%81%D1%83" title="24-гадзінны фармат часу – Belarusian (Taraškievica orthography)" lang="be-tarask" hreflang="be-tarask" data-title="24-гадзінны фармат часу" data-language-autonym="Беларуская (тарашкевіца)" data-language-local-name="Belarusian (Taraškievica orthography)" class="interlanguage-link-target"><span>Беларуская (тарашкевіца)</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/24-%D1%87%D0%B0%D1%81%D0%BE%D0%B2_%D1%87%D0%B0%D1%81%D0%BE%D0%B2%D0%BD%D0%B8%D0%BA" title="24-часов часовник – Bulgarian" lang="bg" hreflang="bg" data-title="24-часов часовник" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Sistema_horari_de_24_hores" title="Sistema horari de 24 hores – Catalan" lang="ca" hreflang="ca" data-title="Sistema horari de 24 hores" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cv mw-list-item"><a href="https://cv.wikipedia.org/wiki/%D0%A2%D0%B0%D0%BB%C4%83%D0%BA_%D0%B2%C4%83%D1%85%C4%83%D1%87%C4%95" title="Талăк вăхăчĕ – Chuvash" lang="cv" hreflang="cv" data-title="Талăк вăхăчĕ" data-language-autonym="Чӑвашла" data-language-local-name="Chuvash" class="interlanguage-link-target"><span>Чӑвашла</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/24-Stunden-Z%C3%A4hlung" title="24-Stunden-Zählung – German" lang="de" hreflang="de" data-title="24-Stunden-Zählung" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Sistema_horario_de_24_horas" title="Sistema horario de 24 horas – Spanish" lang="es" hreflang="es" data-title="Sistema horario de 24 horas" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/24-hora_sistemo" title="24-hora sistemo – Esperanto" lang="eo" hreflang="eo" data-title="24-hora sistemo" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B3%D8%A7%D8%B9%D8%AA_%D8%A8%DB%8C%D8%B3%D8%AA%E2%80%8C%D9%88%DA%86%D9%87%D8%A7%D8%B1_%D8%B3%D8%A7%D8%B9%D8%AA%D9%87" title="ساعت بیست‌وچهار ساعته – Persian" lang="fa" hreflang="fa" data-title="ساعت بیست‌وچهار ساعته" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Syst%C3%A8me_horaire_sur_24_heures" title="Système horaire sur 24 heures – French" lang="fr" hreflang="fr" data-title="Système horaire sur 24 heures" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/24%EC%8B%9C%EA%B0%84%EC%A0%9C" title="24시간제 – Korean" lang="ko" hreflang="ko" data-title="24시간제" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D4%BA%D5%A1%D5%B4%D5%A1%D5%B6%D5%B8%D6%82%D5%B6%D5%B6%D5%A5%D6%80" title="Ժամանուններ – Armenian" lang="hy" hreflang="hy" data-title="Ժամանուններ" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/24_%E0%A4%98%E0%A4%82%E0%A4%9F%E0%A5%87_%E0%A4%95%E0%A5%80_%E0%A4%98%E0%A4%A1%E0%A4%BC%E0%A5%80" title="24 घंटे की घड़ी – Hindi" lang="hi" hreflang="hi" data-title="24 घंटे की घड़ी" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Sistem_24_jam" title="Sistem 24 jam – Indonesian" lang="id" hreflang="id" data-title="Sistem 24 jam" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Sistema_orario_a_24_ore" title="Sistema orario a 24 ore – Italian" lang="it" hreflang="it" data-title="Sistema orario a 24 ore" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%A9%D7%A2%D7%95%D7%9F_%D7%91%D7%9F_24_%D7%A9%D7%A2%D7%95%D7%AA" title="שעון בן 24 שעות – Hebrew" lang="he" hreflang="he" data-title="שעון בן 24 שעות" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Jam_24_jam" title="Jam 24 jam – Malay" lang="ms" hreflang="ms" data-title="Jam 24 jam" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/24%E6%99%82%E5%88%B6" title="24時制 – Japanese" lang="ja" hreflang="ja" data-title="24時制" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/24-timersklokke" title="24-timersklokke – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="24-timersklokke" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-qu mw-list-item"><a href="https://qu.wikipedia.org/wiki/Uras" title="Uras – Quechua" lang="qu" hreflang="qu" data-title="Uras" data-language-autonym="Runa Simi" data-language-local-name="Quechua" class="interlanguage-link-target"><span>Runa Simi</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/24-%D1%87%D0%B0%D1%81%D0%BE%D0%B2%D0%BE%D0%B9_%D1%84%D0%BE%D1%80%D0%BC%D0%B0%D1%82_%D0%B2%D1%80%D0%B5%D0%BC%D0%B5%D0%BD%D0%B8" title="24-часовой формат времени – Russian" lang="ru" hreflang="ru" data-title="24-часовой формат времени" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/24-hour_clock" title="24-hour clock – Simple English" lang="en-simple" hreflang="en-simple" data-title="24-hour clock" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/24_tunnin_kello" title="24 tunnin kello – Finnish" lang="fi" hreflang="fi" data-title="24 tunnin kello" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/24-timmarsklocka" title="24-timmarsklocka – Swedish" lang="sv" hreflang="sv" data-title="24-timmarsklocka" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tl mw-list-item"><a href="https://tl.wikipedia.org/wiki/24-oras_na_orasan" title="24-oras na orasan – Tagalog" lang="tl" hreflang="tl" data-title="24-oras na orasan" data-language-autonym="Tagalog" data-language-local-name="Tagalog" class="interlanguage-link-target"><span>Tagalog</span></a></li><li class="interlanguage-link interwiki-tg badge-Q70893996 mw-list-item" title=""><a href="https://tg.wikipedia.org/wiki/%D0%A8%D0%B0%D0%B1%D0%BE%D0%BD%D0%B0%D1%80%D3%AF%D0%B7" title="Шабонарӯз – Tajik" lang="tg" hreflang="tg" data-title="Шабонарӯз" data-language-autonym="Тоҷикӣ" data-language-local-name="Tajik" class="interlanguage-link-target"><span>Тоҷикӣ</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/24_saatlik_zaman" title="24 saatlik zaman – Turkish" lang="tr" hreflang="tr" data-title="24 saatlik zaman" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-tyv mw-list-item"><a href="https://tyv.wikipedia.org/wiki/%D0%92%D1%80%D0%B5%D0%BC%D1%8F_%D1%81%D1%83%D1%82%D0%BE%D0%BA" title="Время суток – Tuvinian" lang="tyv" hreflang="tyv" data-title="Время суток" data-language-autonym="Тыва дыл" data-language-local-name="Tuvinian" class="interlanguage-link-target"><span>Тыва дыл</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/24-%D0%B3%D0%BE%D0%B4%D0%B8%D0%BD%D0%BD%D0%B8%D0%B9_%D1%84%D0%BE%D1%80%D0%BC%D0%B0%D1%82_%D1%87%D0%B0%D1%81%D1%83" title="24-годинний формат часу – Ukrainian" lang="uk" hreflang="uk" data-title="24-годинний формат часу" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/24_gi%E1%BB%9D" title="24 giờ – Vietnamese" lang="vi" hreflang="vi" data-title="24 giờ" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E5%BB%BF%E5%9B%9B%E5%B0%8F%E6%99%82%E5%88%B6" title="廿四小時制 – Cantonese" lang="yue" hreflang="yue" data-title="廿四小時制" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target"><span>粵語</span></a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/%E4%BA%8C%E5%8D%81%E5%9B%9B%E5%B0%8F%E6%99%82%E5%88%B6" title="二十四小時制 – Chinese" lang="zh" hreflang="zh" data-title="二十四小時制" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li> </ul> <div class="after-portlet 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<div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Timekeeping convention</div> <p class="mw-empty-elt"> </p> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:24_hour_analog_clock_rua_24_horas_curitiba_brasil.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/04/24_hour_analog_clock_rua_24_horas_curitiba_brasil.jpg/220px-24_hour_analog_clock_rua_24_horas_curitiba_brasil.jpg" decoding="async" width="220" height="164" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/04/24_hour_analog_clock_rua_24_horas_curitiba_brasil.jpg/330px-24_hour_analog_clock_rua_24_horas_curitiba_brasil.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/04/24_hour_analog_clock_rua_24_horas_curitiba_brasil.jpg/440px-24_hour_analog_clock_rua_24_horas_curitiba_brasil.jpg 2x" data-file-width="2264" data-file-height="1683" /></a><figcaption>A public 24-hour clock in <a href="/wiki/Curitiba" title="Curitiba">Curitiba</a>, Brazil, with the hour hand on the outside and the minute hand on the inside.</figcaption></figure> <p>The modern <b>24-hour clock</b> is the convention of <a href="/wiki/Timekeeping" class="mw-redirect" title="Timekeeping">timekeeping</a> in which the <a href="/wiki/Day" title="Day">day</a> runs from <a href="/wiki/Midnight" title="Midnight">midnight</a> to midnight and is divided into 24 hours. This is indicated by the hours (and minutes) passed since midnight, from <span class="nowrap">00(:00)</span> to <span class="nowrap">23(:59)</span>, with <span class="nowrap">24(:00)</span> as an option to indicate the end of the day. This system, as opposed to the <a href="/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a>, is the most commonly used time notation in the world today,<sup id="cite_ref-CLDR_1-0" class="reference"><a href="#cite_note-CLDR-1"><span class="cite-bracket">[</span>A<span class="cite-bracket">]</span></a></sup> and is used by the international standard <a href="/wiki/ISO_8601" title="ISO 8601">ISO 8601</a>.<sup id="cite_ref-iso8601_2-0" class="reference"><a href="#cite_note-iso8601-2"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> </p><p>A number of countries, particularly English speaking, use the 12-hour clock, or a mixture of the 24- and 12-hour time systems. In countries where the 12-hour clock is dominant, some professions prefer to use the 24-hour clock. For example, in the practice of <a href="/wiki/Medicine" title="Medicine">medicine</a>, the 24-hour clock is generally used in documentation of care as it prevents any <a href="/wiki/Ambiguity" title="Ambiguity">ambiguity</a> as to when events occurred in a patient's <a href="/wiki/Medical_history" title="Medical history">medical history</a>.<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Description">Description</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=1" title="Edit section: Description"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <table class="wikitable" style="float:right; margin:0.5em 0 0.5em 1em; font-size:95%;"> <tbody><tr> <th>24-hour clock</th> <th><a href="/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a> </th></tr> <tr> <td>00:00</td> <td>12:00 midnight<sup id="cite_ref-noonmidnight_4-0" class="reference"><a href="#cite_note-noonmidnight-4"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup><br />12:00 a.m. (start of the day) </td></tr> <tr> <td>01:00</td> <td>1:00 a.m. </td></tr> <tr> <td>02:00</td> <td>2:00 a.m. </td></tr> <tr> <td>03:00</td> <td>3:00 a.m. </td></tr> <tr> <td>04:00</td> <td>4:00 a.m. </td></tr> <tr> <td>05:00</td> <td>5:00 a.m. </td></tr> <tr> <td>06:00</td> <td>6:00 a.m. </td></tr> <tr> <td>07:00</td> <td>7:00 a.m. </td></tr> <tr> <td>08:00</td> <td>8:00 a.m. </td></tr> <tr> <td>09:00</td> <td>9:00 a.m. </td></tr> <tr> <td>10:00</td> <td>10:00 a.m. </td></tr> <tr> <td>11:00</td> <td>11:00 a.m. </td></tr> <tr> <td>12:00</td> <td>12:00 noon<sup id="cite_ref-noonmidnight_4-1" class="reference"><a href="#cite_note-noonmidnight-4"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup><br />12:00 p.m. </td></tr> <tr> <td>13:00</td> <td>1:00 p.m. </td></tr> <tr> <td>14:00</td> <td>2:00 p.m. </td></tr> <tr> <td>15:00</td> <td>3:00 p.m. </td></tr> <tr> <td>16:00</td> <td>4:00 p.m. </td></tr> <tr> <td>17:00</td> <td>5:00 p.m. </td></tr> <tr> <td>18:00</td> <td>6:00 p.m. </td></tr> <tr> <td>19:00</td> <td>7:00 p.m. </td></tr> <tr> <td>20:00</td> <td>8:00 p.m. </td></tr> <tr> <td>21:00</td> <td>9:00 p.m. </td></tr> <tr> <td>22:00</td> <td>10:00 p.m. </td></tr> <tr> <td>23:00</td> <td>11:00 p.m. </td></tr> <tr> <td>24:00 equals<br />00:00 next day</td> <td>12:00 midnight<sup id="cite_ref-noonmidnight_4-2" class="reference"><a href="#cite_note-noonmidnight-4"><span class="cite-bracket">[</span>a<span class="cite-bracket">]</span></a></sup><br />(end of the day) </td></tr> <tr> <td colspan="3"><style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-lower-alpha"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-noonmidnight-4"><span class="mw-cite-backlink">^ <a href="#cite_ref-noonmidnight_4-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-noonmidnight_4-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-noonmidnight_4-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text">See: <a href="/wiki/12-hour_clock#Confusion_at_noon_and_midnight" title="12-hour clock">12-hour clock § Confusion at noon and midnight</a></span> </li> </ol></div></div> </td></tr></tbody></table> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:12_24_Hours_World_Map.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/8a/12_24_Hours_World_Map.svg/220px-12_24_Hours_World_Map.svg.png" decoding="async" width="220" height="112" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/8a/12_24_Hours_World_Map.svg/330px-12_24_Hours_World_Map.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/8a/12_24_Hours_World_Map.svg/440px-12_24_Hours_World_Map.svg.png 2x" data-file-width="2754" data-file-height="1398" /></a><figcaption>World map showing the usage of 12 or 24-hour clock in different countries<style data-mw-deduplicate="TemplateStyles:r981673959">.mw-parser-output .legend{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .legend-color{display:inline-block;min-width:1.25em;height:1.25em;line-height:1.25;margin:1px 0;text-align:center;border:1px solid black;background-color:transparent;color:black}.mw-parser-output .legend-text{}</style><div class="legend"><span class="legend-color mw-no-invert" style="background-color:#f0027f; color:black;"> </span> 24-hour</div><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r981673959"><div class="legend"><span class="legend-color mw-no-invert" style="background-color:#990052; color:white;"> </span> 24-hour (12-hour orally)</div><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r981673959"><div class="legend"><span class="legend-color mw-no-invert" style="background-color:#7fc97f; color:black;"> </span> Both in common use</div><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r981673959"><div class="legend"><span class="legend-color mw-no-invert" style="background-color:#386cb0; color:white;"> </span> 12-hour</div></figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Digital_clock_in_THSR_Miaoli_Station.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Digital_clock_in_THSR_Miaoli_Station.jpg/220px-Digital_clock_in_THSR_Miaoli_Station.jpg" decoding="async" width="220" height="165" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Digital_clock_in_THSR_Miaoli_Station.jpg/330px-Digital_clock_in_THSR_Miaoli_Station.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/e/ea/Digital_clock_in_THSR_Miaoli_Station.jpg/440px-Digital_clock_in_THSR_Miaoli_Station.jpg 2x" data-file-width="4032" data-file-height="3024" /></a><figcaption>24-hour digital clock in <a href="/wiki/Miaoli_HSR_station" title="Miaoli HSR station">Miaoli HSR station</a>.</figcaption></figure> <p>A time of day is written in the 24-hour notation in the form hh:mm (for example 01:23) or hh:mm:ss (for example, 01:23:45), where hh (00 to 23) is the number of full hours that have passed since <a href="/wiki/Midnight" title="Midnight">midnight</a>, mm (00 to 59) is the number of full minutes that have passed since the last full hour, and ss (00 to 59) is the number of seconds since the last full minute. To indicate the exact end of the day, hh may take the value 24, with mm and ss taking the value 00. In the case of a <a href="/wiki/Leap_second" title="Leap second">leap second</a>, the value of ss may extend to 60. A leading zero is added for numbers under 10, but it is optional for the hours. The leading zero is very commonly used in computer applications, and always used when a specification requires it (for example, <a href="/wiki/ISO_8601" title="ISO 8601">ISO 8601</a>). </p><p>Where subsecond resolution is required, the seconds can be a <a href="/wiki/Decimal#Decimal_fractions" title="Decimal">decimal fraction</a>; that is, the fractional part follows a decimal dot or comma, as in 01:23:45.678. The most commonly used separator symbol between hours, minutes and seconds is the <a href="/wiki/Colon_(punctuation)" title="Colon (punctuation)">colon</a>, which is also the symbol used in ISO 8601. In the past, some European countries used the <a href="/wiki/Full_stop" title="Full stop">dot on the line</a> as a separator, but most national standards on time notation have since then been changed to the international standard colon. In some contexts (including some computer protocols and military time), no separator is used and times are written as, for example, "2359". </p> <div class="mw-heading mw-heading3"><h3 id="Midnight_00:00_and_24:00">Midnight 00:00 and 24:00</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=2" title="Edit section: Midnight 00:00 and 24:00"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><div role="note" class="hatnote navigation-not-searchable">"23:59" redirects here. For the Christian metal album, see <a href="/wiki/Veni_Domine#Discography" title="Veni Domine">Veni Domine § Discography</a>. For the film, see <a href="/wiki/23:59_(film)" title="23:59 (film)">23:59 (film)</a>.</div> <p>In the 24-hour time notation, the day begins at midnight, 00:00 or 0:00, and the last minute of the day begins at 23:59. Where convenient, the notation 24:00 may also be used to refer to midnight at the end of a given date<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> — that is, 24:00 of one day is the same time as 00:00 of the following day. </p><p>The notation 24:00 mainly serves to refer to the exact end of a day in a time interval. A typical usage is giving opening hours ending at midnight (e.g. "00:00–24:00", "07:00–24:00"). Similarly, some bus and train timetables show 00:00 as departure time and 24:00 as arrival time. Legal contracts often run from the start date at 00:00 until the end date at 24:00. </p><p>While the 24-hour notation unambiguously distinguishes between midnight at the start (00:00) and end (24:00) of any given date, there is no commonly accepted distinction among users of the 12-hour notation. <a href="/wiki/Style_guide" title="Style guide">Style guides</a> and military communication regulations in some English-speaking countries discourage the use of 24:00 even in the 24-hour notation, and recommend reporting times near midnight as 23:59 or 00:01 instead.<sup id="cite_ref-acp121_6-0" class="reference"><a href="#cite_note-acp121-6"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> Sometimes the use of 00:00 is also avoided.<sup id="cite_ref-acp121_6-1" class="reference"><a href="#cite_note-acp121-6"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> In variance with this, as of 2010, the correspondence manual for the <a href="/wiki/United_States_Navy" title="United States Navy">United States Navy</a> and <a href="/wiki/United_States_Marine_Corps" title="United States Marine Corps">United States Marine Corps</a> formerly specified 0001 to 2400.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> The manual was updated in June 2015 to use 0000 to 2359.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Times_after_24:00">Times after 24:00</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=3" title="Edit section: Times after 24:00"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Date_and_time_notation_in_Japan#Time" title="Date and time notation in Japan">Date and time notation in Japan § Time</a></div> <p>Time-of-day notations beyond 24:00 (such as 24:01 or 25:00 instead of 00:01 or 01:00) are not commonly used and not covered by the relevant standards. However, they have been used occasionally in some special contexts in the United Kingdom, France, Spain, Canada, Japan, South Korea, Hong Kong, and China where business hours extend beyond midnight, such as broadcast television production and scheduling. The <a href="/wiki/General_Transit_Feed_Specification" class="mw-redirect" title="General Transit Feed Specification">GTFS</a> public transport schedule listings file format has the concept of service days and expects times beyond 24:00 for trips that run after midnight.<sup id="cite_ref-9" class="reference"><a href="#cite_note-9"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Computer_support">Computer support</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=4" title="Edit section: Computer support"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>In most countries, computers by default show the time in 24-hour notation. For example, <a href="/wiki/Microsoft_Windows" title="Microsoft Windows">Microsoft Windows</a> and <a href="/wiki/MacOS" title="MacOS">macOS</a> activate the 12-hour notation by default only if a computer is in a handful of specific language and region settings. The 24-hour system is commonly used in text-based interfaces. <a href="/wiki/POSIX" title="POSIX">POSIX</a> programs such as <a href="/wiki/Ls" title="Ls">ls</a> default to displaying timestamps in 24-hour format. </p> <div class="mw-heading mw-heading3"><h3 id="Military_time">Military time</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=5" title="Edit section: Military time"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:24-Hour_Clock_Aboard_the_USS_Midway_(8727193240).jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/24-Hour_Clock_Aboard_the_USS_Midway_%288727193240%29.jpg/220px-24-Hour_Clock_Aboard_the_USS_Midway_%288727193240%29.jpg" decoding="async" width="220" height="146" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/24-Hour_Clock_Aboard_the_USS_Midway_%288727193240%29.jpg/330px-24-Hour_Clock_Aboard_the_USS_Midway_%288727193240%29.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/63/24-Hour_Clock_Aboard_the_USS_Midway_%288727193240%29.jpg/440px-24-Hour_Clock_Aboard_the_USS_Midway_%288727193240%29.jpg 2x" data-file-width="3672" data-file-height="2438" /></a><figcaption>24-hour clock as seen on the <a href="/wiki/USS_Midway_(CV-41)" title="USS Midway (CV-41)">USS Midway</a>.</figcaption></figure> <p>In <a href="/wiki/American_English" title="American English">American English</a>, the term <i>military time</i> is a synonym for the 24-hour clock.<sup id="cite_ref-10" class="reference"><a href="#cite_note-10"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> In the US, the time of day is customarily given almost exclusively using the 12-hour clock notation, which counts the hours of the day as 12, 1, ..., 11 with suffixes <i>a.m.</i> and <i>p.m.</i> distinguishing the two <a href="/wiki/Day" title="Day">diurnal</a> repetitions of this sequence. The 24-hour clock is commonly used there only in some specialist areas (military, aviation, navigation, tourism, meteorology, astronomy, computing, logistics, emergency services, hospitals), where the <a href="/wiki/12-hour_clock#Confusion_at_noon_and_midnight" title="12-hour clock">ambiguities of the 12-hour notation</a> are deemed too inconvenient, cumbersome, or dangerous. </p><p>Military usage, as agreed between the United States and allied English-speaking military forces,<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> differs in some respects from other twenty-four-hour time systems: </p> <ul><li>No hours/minutes separator is used when writing the time, and a <a href="/wiki/Nautical_time#Letter_suffixes" title="Nautical time">letter designating the time zone</a> is appended (for example "0340Z").</li> <li><a href="/wiki/Leading_zero" title="Leading zero">Leading zeros</a> are always written out and are required to be spoken, so 5:43 a.m. is spoken "zero five forty-three" (casually) or "zero five four three" (military radio), as opposed to "five forty-three" or "five four three".</li> <li><a href="/wiki/List_of_military_time_zones" class="mw-redirect" title="List of military time zones">Military time zones</a> are lettered and given word designations from the <a href="/wiki/NATO_phonetic_alphabet" title="NATO phonetic alphabet">NATO phonetic alphabet</a>. For example, in <a href="/wiki/Eastern_Time_Zone" title="Eastern Time Zone">US Eastern Standard Time</a> (UTC−5), which is designated time zone R, 2:00 a.m. is written "0200R" and spoken "zero two hundred Romeo".</li> <li>Local time is designated as zone J or "<a href="/wiki/NATO_phonetic_alphabet" title="NATO phonetic alphabet">Juliett</a>". "1200J" ("twelve hundred Juliett") is noon local time.</li> <li><a href="/wiki/Greenwich_Mean_Time" title="Greenwich Mean Time">Greenwich Mean Time</a> (GMT) or <a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">Coordinated Universal Time</a> (UTC) is designated time zone Z, and thus called "Zulu time". (When used as a modern time zone, in practice, GMT and UTC coincide. For other purposes there may be a difference of about a second.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup>)</li> <li>Hours are always "hundred", never "thousand"; 1000 is "ten hundred" not "one thousand"; 2000 is "twenty hundred" not "two thousand".</li></ul> <div class="mw-heading mw-heading2"><h2 id="History">History</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=6" title="Edit section: History"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Florence-Duomo-Clock.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Florence-Duomo-Clock.jpg/220px-Florence-Duomo-Clock.jpg" decoding="async" width="220" height="220" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Florence-Duomo-Clock.jpg/330px-Florence-Duomo-Clock.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/4/4a/Florence-Duomo-Clock.jpg/440px-Florence-Duomo-Clock.jpg 2x" data-file-width="448" data-file-height="447" /></a><figcaption><a href="/wiki/Paolo_Uccello" title="Paolo Uccello">Paolo Uccello</a>'s <i>Face with Four Prophets/Evangelists</i> (1443) in <a href="/wiki/Florence_Cathedral" title="Florence Cathedral">Florence Cathedral</a></figcaption></figure> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Clock_24_J.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Clock_24_J.jpg/220px-Clock_24_J.jpg" decoding="async" width="220" height="218" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Clock_24_J.jpg/330px-Clock_24_J.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Clock_24_J.jpg/440px-Clock_24_J.jpg 2x" data-file-width="2181" data-file-height="2160" /></a><figcaption>The 24-hour tower clock in <a href="/wiki/Venice" title="Venice">Venice</a> that lists hours 1 to 12 twice</figcaption></figure> <p>The first mechanical public clocks introduced in Italy were <a href="/wiki/24-hour_analogue_dial" class="mw-redirect" title="24-hour analogue dial">mechanical 24-hour clocks</a> which counted the 24 hours of the day from one-half hour after sunset to the evening of the following day. The 24th hour was the last hour of day time.<sup id="cite_ref-Rossum_13-0" class="reference"><a href="#cite_note-Rossum-13"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p>From the 14th to the 17th century, two systems of time measurement competed in Europe:<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-15" class="reference"><a href="#cite_note-15"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup> </p> <ul><li>Italian (Bohemian, Old-Bohemian) hours (full-dial): 24 hours system with the day starting after sunset; on the static dial, the 24th hour was on the right side. In Italy, it was prevalently modified to a 4×6 hours system, but some 24-hour dials lasted until the 19th century. The system has spread especially to the Alpine countries, Czech countries and Poland. In Bohemia, this system was finally banned in 1621 after the <a href="/wiki/Battle_of_White_Mountain" title="Battle of White Mountain">defeat on White Mountain</a>. The Prague Astronomical Clock struck according to the Old Bohemian Clock until its destruction in 1945. The variant with counting from dawn is also rarely documented and used, e.g. on a 16th-century cabinet clock in the Vienna Art-History Museum.<sup id="cite_ref-16" class="reference"><a href="#cite_note-16"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup></li> <li>German (Gallic) hours (half-dial): 2×12 hour system starting at midnight and restarted at noon. It is typical with the 12-hour dial with 12 at the top.</li></ul> <p>The modern 24-hour system is a late-19th century adaptation of the German midnight-starting system, and then prevailed in the world with the exception of some Anglophone countries. </p><p>Striking clocks had to produce 300 strokes each day, which required a lot of rope, and wore out the mechanism quickly, so some localities switched to ringing sequences of 1 to 12 twice (156 strokes), or even 1 to 6 repeated four times (84 strokes).<sup id="cite_ref-Rossum_13-1" class="reference"><a href="#cite_note-Rossum-13"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p><p><a href="/wiki/Sandford_Fleming" title="Sandford Fleming">Sandford Fleming</a>, the engineer-in-chief of the Canadian <a href="/wiki/Intercolonial_Railway" title="Intercolonial Railway">Intercolonial Railway</a>, was an early proponent of using the 24-hour clock as part of a programme to reform timekeeping, which also included establishing <a href="/wiki/Time_zone" title="Time zone">time zones</a> and a standard <a href="/wiki/Prime_meridian" title="Prime meridian">prime meridian</a>.<sup id="cite_ref-Fleming_17-0" class="reference"><a href="#cite_note-Fleming-17"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-Creet_18-0" class="reference"><a href="#cite_note-Creet-18"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> At the <a href="/wiki/International_Meridian_Conference" title="International Meridian Conference">International Meridian Conference</a> in 1884, the following resolution was adopted by the conference:<sup id="cite_ref-imc_19-0" class="reference"><a href="#cite_note-imc-19"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> <style data-mw-deduplicate="TemplateStyles:r1244412712">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}}</style><blockquote class="templatequote"> <p>That this universal day is to be a mean solar day; is to begin for all the world at the moment of midnight of the initial meridian coinciding with the beginning of the civil day and date of that meridian, and is to be counted from zero up to twenty-four hours.<sup id="cite_ref-imc_19-1" class="reference"><a href="#cite_note-imc-19"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup> </p> </blockquote> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Greenwich_clock_1-manipulated.jpg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/6/61/Greenwich_clock_1-manipulated.jpg/220px-Greenwich_clock_1-manipulated.jpg" decoding="async" width="220" height="196" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/61/Greenwich_clock_1-manipulated.jpg/330px-Greenwich_clock_1-manipulated.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/61/Greenwich_clock_1-manipulated.jpg/440px-Greenwich_clock_1-manipulated.jpg 2x" data-file-width="2215" data-file-height="1972" /></a><figcaption>The <a href="/wiki/Shepherd_Gate_Clock" title="Shepherd Gate Clock">Shepherd Gate Clock</a> with <a href="/wiki/Roman_numerals" title="Roman numerals">Roman numerals</a> up to XXIII (23) and 0 for midnight, in Greenwich</figcaption></figure> <p>The <a href="/wiki/Canadian_Pacific_Railway" title="Canadian Pacific Railway">Canadian Pacific Railway</a> was among the first organisations to adopt the 24-hour clock, at <a href="/wiki/Midsummer" title="Midsummer">midsummer</a> 1886.<sup id="cite_ref-Fleming_17-1" class="reference"><a href="#cite_note-Fleming-17"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-20" class="reference"><a href="#cite_note-20"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> A report by a government committee in the United Kingdom noted Italy as the first country among those mentioned to adopt 24-hour time nationally, in 1893.<sup id="cite_ref-baird_21-0" class="reference"><a href="#cite_note-baird-21"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> Other European countries followed: France adopted it in 1912 (the French army in 1909), followed by Denmark (1916), and Greece (1917). By 1920, Spain, Portugal, Belgium, and Switzerland had switched, followed by Turkey (1925), and Germany (1927). By the early 1920s, many countries in Latin America had also adopted the 24-hour clock.<sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> Some of the railways in India had switched before the outbreak of the war.<sup id="cite_ref-baird_21-1" class="reference"><a href="#cite_note-baird-21"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> </p><p>During <a href="/wiki/World_War_I" title="World War I">World War I</a>, the British Royal Navy adopted the 24-hour clock in 1915, and the Allied armed forces followed soon after,<sup id="cite_ref-baird_21-2" class="reference"><a href="#cite_note-baird-21"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> with the British Army switching officially in 1918.<sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup> The Canadian armed forces first started to use the 24-hour clock in late 1917.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup> In 1920, the United States Navy was the first United States organisation to adopt the system; the <a href="/wiki/United_States_Army" title="United States Army">United States Army</a>, however, did not officially adopt the 24-hour clock until 1 July 1942.<sup id="cite_ref-BrownsvilleHerald1942_25-0" class="reference"><a href="#cite_note-BrownsvilleHerald1942-25"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> <sup id="cite_ref-ElPaso1942_26-0" class="reference"><a href="#cite_note-ElPaso1942-26"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup> </p><p>The use of the <a href="/wiki/Date_and_time_notation_in_the_United_Kingdom#Time" title="Date and time notation in the United Kingdom">24-hour clock in the United Kingdom</a> has grown steadily since the beginning of the 20th century, although attempts to make the system official failed more than once.<sup id="cite_ref-counting-time_27-0" class="reference"><a href="#cite_note-counting-time-27"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> In 1934, the <a href="/wiki/BBC" title="BBC">British Broadcasting Corporation</a> (BBC) switched to the 24-hour clock for broadcast announcements and programme listings. The experiment was halted after five months following a lack of enthusiasm from the public, and the BBC continued using the 12-hour clock.<sup id="cite_ref-counting-time_27-1" class="reference"><a href="#cite_note-counting-time-27"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> In the same year, <a href="/wiki/Pan_American_World_Airways" class="mw-redirect" title="Pan American World Airways">Pan American World Airways Corporation</a> and <a href="/wiki/Western_Airlines" title="Western Airlines">Western Airlines</a> in the United States both adopted the 24-hour clock.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> In modern times, the BBC uses a mixture of both the 12-hour and the 24-hour clock.<sup id="cite_ref-counting-time_27-2" class="reference"><a href="#cite_note-counting-time-27"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> <a href="/wiki/British_Rail" title="British Rail">British Rail</a>, <a href="/wiki/London_Transport_(brand)" title="London Transport (brand)">London Transport</a>, and the <a href="/wiki/London_Underground" title="London Underground">London Underground</a> switched to the 24-hour clock for timetables in 1964.<sup id="cite_ref-counting-time_27-3" class="reference"><a href="#cite_note-counting-time-27"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> A mixture of the 12- and 24-hour clocks similarly prevails in other English-speaking <a href="/wiki/Commonwealth_of_Nations" title="Commonwealth of Nations">Commonwealth</a> countries: French speakers have adopted the <a href="/wiki/Date_and_time_notation_in_Canada#Time" title="Date and time notation in Canada">24-hour clock in Canada</a> much more broadly than English speakers, and <a href="/wiki/Date_and_time_notation_in_Australia#Time" title="Date and time notation in Australia">Australia</a> as well as <a href="/wiki/Date_and_time_notation_in_New_Zealand#Time" title="Date and time notation in New Zealand">New Zealand</a> also use both systems. </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=7" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1184024115">.mw-parser-output .div-col{margin-top:0.3em;column-width:30em}.mw-parser-output .div-col-small{font-size:90%}.mw-parser-output .div-col-rules{column-rule:1px solid #aaa}.mw-parser-output .div-col dl,.mw-parser-output .div-col ol,.mw-parser-output .div-col ul{margin-top:0}.mw-parser-output .div-col li,.mw-parser-output .div-col dd{page-break-inside:avoid;break-inside:avoid-column}</style><div class="div-col" style="column-width: 23em;"> <ul><li><a href="/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a></li> <li><a href="/wiki/24-hour_analog_dial" title="24-hour analog dial">24-hour analog dial</a></li> <li><a href="/wiki/Clock" title="Clock">Clock</a></li> <li><a href="/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="/wiki/Decimal_time" title="Decimal time">Decimal time</a></li> <li><a href="/wiki/Hindu_units_of_time" title="Hindu units of time">Hindu units of time</a></li> <li><a href="/wiki/Italian_six-hour_clock" title="Italian six-hour clock">Italian six-hour clock</a></li> <li><a href="/wiki/List_of_military_time_zones" class="mw-redirect" title="List of military time zones">List of military time zones</a></li> <li><a href="/wiki/Metric_time" title="Metric time">Metric time</a></li> <li><a href="/wiki/Thai_six-hour_clock" title="Thai six-hour clock">Thai six-hour clock</a></li> <li><a href="/wiki/Time" title="Time">Time</a></li> <li><a href="/wiki/Traditional_Chinese_timekeeping" title="Traditional Chinese timekeeping">Traditional Chinese timekeeping</a></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=8" title="Edit section: Notes"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist reflist-upper-alpha"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-CLDR-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-CLDR_1-0">^</a></b></span> <span class="reference-text">See the <a href="/wiki/Common_Locale_Data_Repository" title="Common Locale Data Repository">Common Locale Data Repository</a> for detailed data about the preferred date and time notations used across the world, as well the <a href="/wiki/Locale_(computer_software)" title="Locale (computer software)">locale</a> settings of major computer <a href="/wiki/Operating_system" title="Operating system">operating systems</a>, and the article <a href="/wiki/Date_and_time_representation_by_country" title="Date and time representation by country">Date and time representation by country</a>.</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=9" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist"> <div class="mw-references-wrap mw-references-columns"><ol class="references"> <li id="cite_note-iso8601-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-iso8601_2-0">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation cs1"><a rel="nofollow" class="external text" href="https://www.iso.org/standard/40874.html"><i>ISO 8601:2004 – Data elements and interchange formats – Information interchange – Representation of dates and times</i></a> (3rd ed.). 2004.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=ISO+8601%3A2004+%E2%80%93+Data+elements+and+interchange+formats+%E2%80%93+Information+interchange+%E2%80%93+Representation+of+dates+and+times&rft.edition=3rd&rft.date=2004&rft_id=https%3A%2F%2Fwww.iso.org%2Fstandard%2F40874.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFPickarGrahamSwartSwedish2011" class="citation book cs1">Pickar, Gloria D.; Graham, Hope; Swart, Beth; Swedish, Margaret (2011). <i>Dosage calculations</i> (2nd Canadian ed.). Toronto: Nelson Education. p. 60. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/9780176502591" title="Special:BookSources/9780176502591"><bdi>9780176502591</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Dosage+calculations&rft.place=Toronto&rft.pages=60&rft.edition=2nd+Canadian&rft.pub=Nelson+Education&rft.date=2011&rft.isbn=9780176502591&rft.aulast=Pickar&rft.aufirst=Gloria+D.&rft.au=Graham%2C+Hope&rft.au=Swart%2C+Beth&rft.au=Swedish%2C+Margaret&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation cs1"><a rel="nofollow" class="external text" href="https://www.iso.org/standard/40874.html"><i>ISO 8601:2004 – Data elements and interchange formats – Information interchange – Representation of dates and times</i></a> (3rd ed.). 2004. Clause 4.2.3 "Midnight".</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=ISO+8601%3A2004+%E2%80%93+Data+elements+and+interchange+formats+%E2%80%93+Information+interchange+%E2%80%93+Representation+of+dates+and+times&rft.pages=Clause+4.2.3+%22Midnight%22&rft.edition=3rd&rft.date=2004&rft_id=https%3A%2F%2Fwww.iso.org%2Fstandard%2F40874.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-acp121-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-acp121_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-acp121_6-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20110807210103/http://jcs.dtic.mil/j6/cceb/acps/acp121/ACP121I.pdf"><i>Communication instructions – General</i></a> <span class="cs1-format">(PDF)</span>. Combined Communications-Electronics Board. October 2010. p. 3-6. ACP 121(I). Archived from <a rel="nofollow" class="external text" href="http://jcs.dtic.mil/j6/cceb/acps/acp121/ACP121I.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 7 August 2011.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Communication+instructions+%E2%80%93+General&rft.pages=3%26%2345%3B6&rft.pub=Combined+Communications-Electronics+Board&rft.date=2010-10&rft_id=http%3A%2F%2Fjcs.dtic.mil%2Fj6%2Fcceb%2Facps%2Facp121%2FACP121I.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="http://www.marforres.marines.mil/Portals/116/Docs/G-1/AAU/AAUDocuments/CORRESPONDENCE%20MANUAL.pdf"><i>Department of the Navy Correspondence Manual</i></a> <span class="cs1-format">(PDF)</span>. <a href="/wiki/United_States_Department_of_the_Navy" title="United States Department of the Navy">United States Department of the Navy</a>. March 2010. Chapter 2, Section 5 Paragraph 15. Expressing Military Time. SECNAV M-5216.5.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Department+of+the+Navy+Correspondence+Manual&rft.pages=Chapter+2%2C+Section+5+Paragraph+15.+Expressing+Military+Time&rft.pub=United+States+Department+of+the+Navy&rft.date=2010-03&rft_id=http%3A%2F%2Fwww.marforres.marines.mil%2FPortals%2F116%2FDocs%2FG-1%2FAAU%2FAAUDocuments%2FCORRESPONDENCE%2520MANUAL.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation book cs1"><a rel="nofollow" class="external text" href="https://www.marines.mil/Portals/59/Publications/SECNAV%20M%205216.5.pdf"><i>Department of the Navy Correspondence Manual</i></a> <span class="cs1-format">(PDF)</span>. <a href="/wiki/United_States_Department_of_the_Navy" title="United States Department of the Navy">United States Department of the Navy</a>. June 2015. Chapter 2, Section 5 Paragraph 15. Expressing Military Time. SECNAV M-5216.5.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Department+of+the+Navy+Correspondence+Manual&rft.pages=Chapter+2%2C+Section+5+Paragraph+15.+Expressing+Military+Time&rft.pub=United+States+Department+of+the+Navy&rft.date=2015-06&rft_id=https%3A%2F%2Fwww.marines.mil%2FPortals%2F59%2FPublications%2FSECNAV%2520M%25205216.5.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://developers.google.com/transit/gtfs/reference">"Reference | Static Transit"</a>. <i>Google Developers</i>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Google+Developers&rft.atitle=Reference+%26%23124%3B+Static+Transit&rft_id=https%3A%2F%2Fdevelopers.google.com%2Ftransit%2Fgtfs%2Freference&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation encyclopaedia cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20201112033709/https://www.lexico.com/definition/military_time">"military time"</a>. <i><a href="/wiki/Lexico" title="Lexico">Lexico</a> UK English Dictionary</i>. <a href="/wiki/Oxford_University_Press" title="Oxford University Press">Oxford University Press</a>. Archived from <a rel="nofollow" class="external text" href="http://www.lexico.com/definition/military_time">the original</a> on 12 November 2020.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=military+time&rft.btitle=Lexico+UK+English+Dictionary&rft.pub=Oxford+University+Press&rft_id=http%3A%2F%2Fwww.lexico.com%2Fdefinition%2Fmilitary_time&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20160508202743/http://jcs.dtic.mil/j6/cceb/acps/acp121/ACP121I.pdf">"Communication Instructions General ACP 121(I)"</a> <span class="cs1-format">(PDF)</span>. Archived from <a rel="nofollow" class="external text" href="http://jcs.dtic.mil/j6/cceb/acps/acp121/ACP121I.pdf">the original</a> <span class="cs1-format">(PDF)</span> on 8 May 2016.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Communication+Instructions+General+ACP+121%28I%29&rft_id=http%3A%2F%2Fjcs.dtic.mil%2Fj6%2Fcceb%2Facps%2Facp121%2FACP121I.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGuinot2011" class="citation journal cs1">Guinot, Bernard (August 2011). "Solar time, legal time, time in use". <i>Metrologia</i>. <b>48</b> (4): 185. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2011Metro..48S.181G">2011Metro..48S.181G</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1088%2F0026-1394%2F48%2F4%2FS08">10.1088/0026-1394/48/4/S08</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:121852011">121852011</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Metrologia&rft.atitle=Solar+time%2C+legal+time%2C+time+in+use&rft.volume=48&rft.issue=4&rft.pages=185&rft.date=2011-08&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A121852011%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1088%2F0026-1394%2F48%2F4%2FS08&rft_id=info%3Abibcode%2F2011Metro..48S.181G&rft.aulast=Guinot&rft.aufirst=Bernard&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-Rossum-13"><span class="mw-cite-backlink">^ <a href="#cite_ref-Rossum_13-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Rossum_13-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFDohrn-Van_Rossum1996" class="citation book cs1">Dohrn-Van Rossum, Gerhard (1996). <i>History of the Hour. Clock and Modern Temporal Orders</i>. The University of Chicago Press. p. 114. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0226155110" title="Special:BookSources/0226155110"><bdi>0226155110</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=History+of+the+Hour.+Clock+and+Modern+Temporal+Orders&rft.pages=114&rft.pub=The+University+of+Chicago+Press&rft.date=1996&rft.isbn=0226155110&rft.aulast=Dohrn-Van+Rossum&rft.aufirst=Gerhard&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></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">Tomáš Voříšek: <a rel="nofollow" class="external text" href="http://otta.cechove.cz/hodiny.htm">Hodiny německé a české na půl orloje a podle celého orloje</a>, Otta z Losu, last update 2021.</span> </li> <li id="cite_note-15"><span class="mw-cite-backlink"><b><a href="#cite_ref-15">^</a></b></span> <span class="reference-text">Stan. Marušák, Petr Král: <a rel="nofollow" class="external text" href="https://www.orloj.eu/cs/orloj_ctyriadvacetnik.htm">Čtyřiadvacetník</a>, Orloj.eu.</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"><a rel="nofollow" class="external text" href="https://www.orloj.eu/cs/cesky_cas.htm">Český čas s otazníkem</a>, Orloj.eu.</span> </li> <li id="cite_note-Fleming-17"><span class="mw-cite-backlink">^ <a href="#cite_ref-Fleming_17-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Fleming_17-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFFleming1886" class="citation journal cs1">Fleming, Sandford (1886). <a rel="nofollow" class="external text" href="https://library.si.edu/digital-library/book/annualreportofbo18861smit">"Time-reckoning for the twentieth century"</a>. <i>Annual Report of the Board of Regents of the Smithsonian Institution</i> (1): 345–366.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Annual+Report+of+the+Board+of+Regents+of+the+Smithsonian+Institution&rft.atitle=Time-reckoning+for+the+twentieth+century&rft.issue=1&rft.pages=345-366&rft.date=1886&rft.aulast=Fleming&rft.aufirst=Sandford&rft_id=https%3A%2F%2Flibrary.si.edu%2Fdigital-library%2Fbook%2Fannualreportofbo18861smit&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span> Reprinted in 1889: <a rel="nofollow" class="external text" href="https://archive.org/details/timereckoningfor00flem"><i>Time-reckoning for the twentieth century</i></a> at the <a href="/wiki/Internet_Archive" title="Internet Archive">Internet Archive</a>.</span> </li> <li id="cite_note-Creet-18"><span class="mw-cite-backlink"><b><a href="#cite_ref-Creet_18-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCreet1990" class="citation journal cs1">Creet, Mario (1990). <a rel="nofollow" class="external text" href="https://doi.org/10.7202%2F800302ar">"Sandford Fleming and Universal Time"</a>. <i>Scientia Canadensis: Canadian Journal of the History of Science, Technology and Medicine</i>. <b>14</b> (1–2): 66–89. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.7202%2F800302ar">10.7202/800302ar</a></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Scientia+Canadensis%3A+Canadian+Journal+of+the+History+of+Science%2C+Technology+and+Medicine&rft.atitle=Sandford+Fleming+and+Universal+Time&rft.volume=14&rft.issue=1%E2%80%932&rft.pages=66-89&rft.date=1990&rft_id=info%3Adoi%2F10.7202%2F800302ar&rft.aulast=Creet&rft.aufirst=Mario&rft_id=https%3A%2F%2Fdoi.org%2F10.7202%252F800302ar&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-imc-19"><span class="mw-cite-backlink">^ <a href="#cite_ref-imc_19-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-imc_19-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.gutenberg.org/files/17759/17759-h/17759-h.htm">"International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October 1884. Protocols of the proceedings"</a>. Project Gutenberg. 1884<span class="reference-accessdate">. Retrieved <span class="nowrap">30 November</span> 2012</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=International+Conference+Held+at+Washington+for+the+Purpose+of+Fixing+a+Prime+Meridian+and+a+Universal+Day.+October+1884.+Protocols+of+the+proceedings.&rft.pub=Project+Gutenberg&rft.date=1884&rft_id=http%3A%2F%2Fwww.gutenberg.org%2Ffiles%2F17759%2F17759-h%2F17759-h.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></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">The London <i><a href="/wiki/The_Times" title="The Times">Times</a></i> reports on a timetable using the 24-hour clock on a trip from <a href="/wiki/Port_Arthur,_Ontario" title="Port Arthur, Ontario">Port Arthur, Ontario</a>: <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1">"A Canadian Tour". <i>The Times</i>. No. 31880. London. 2 October 1886. col 1–2, p. 8.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=The+Times&rft.atitle=A+Canadian+Tour&rft.issue=31880&rft.pages=col+1-2%2C+p.-8&rft.date=1886-10-02&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-baird-21"><span class="mw-cite-backlink">^ <a href="#cite_ref-baird_21-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-baird_21-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-baird_21-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://discovery.nationalarchives.gov.uk/details/r/D7736214">"Memorandum CAB 24/110/21 (CP 1721), 'Report of the Committee upon the 24 hour method of expressing time'<span class="cs1-kern-right"></span>"</a>. <a href="/wiki/The_National_Archives_(United_Kingdom)" title="The National Archives (United Kingdom)">The National Archives</a>, <a href="/wiki/Kew" title="Kew">Kew</a>, <a href="/wiki/United_Kingdom" title="United Kingdom">United Kingdom</a>. 4 August 1920.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Memorandum+CAB+24%2F110%2F21+%28CP+1721%29%2C+%27Report+of+the+Committee+upon+the+24+hour+method+of+expressing+time%27&rft.place=The+National+Archives%2C+Kew%2C+United+Kingdom&rft.date=1920-08-04&rft_id=http%3A%2F%2Fdiscovery.nationalarchives.gov.uk%2Fdetails%2Fr%2FD7736214&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></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"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://militarytimechart.net/history-24-hour-clock/">"History of the 24-Hour Clock - 24 Hour Time Clock"</a>. <i>Military Time Chart</i>. 24 December 2016<span class="reference-accessdate">. Retrieved <span class="nowrap">27 July</span> 2023</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=Military+Time+Chart&rft.atitle=History+of+the+24-Hour+Clock+-+24+Hour+Time+Clock&rft.date=2016-12-24&rft_id=https%3A%2F%2Fmilitarytimechart.net%2Fhistory-24-hour-clock%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-23"><span class="mw-cite-backlink"><b><a href="#cite_ref-23">^</a></b></span> <span class="reference-text"><i><a href="/wiki/The_Times" title="The Times">The Times</a></i>: 1918 September 19, p. 3.</span> </li> <li id="cite_note-24"><span class="mw-cite-backlink"><b><a href="#cite_ref-24">^</a></b></span> <span class="reference-text">Dancocks, Daniel G. <i>Gallant Canadians: The Story of the 10th Canadian Infantry Battalion 1914–1919</i>.</span> </li> <li id="cite_note-BrownsvilleHerald1942-25"><span class="mw-cite-backlink"><b><a href="#cite_ref-BrownsvilleHerald1942_25-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://newspaperarchive.com/us/texas/brownsville/brownsville-herald/1942/06-26/page-2/">"Army Adopts 24-Hour Clock Plan"</a>. <i>Brownsville Herald</i>. <a href="/wiki/Brownsville,_Texas" title="Brownsville, Texas">Brownsville, Texas</a>. 26 June 1942. p. 2. <q>Effective July 1, the United States Army will adopt the 24-hour clock system for all messages, dispatches, orders and reports, the War Department has announced. Under this new system time will be expressed in a group of four digits ranging from 0000 to 2400. [...] Flying officers at <a href="/wiki/Moore_Air_Force_Base" title="Moore Air Force Base">Moore Field</a> have used the 24-hour clock system for some time. However, its use in official business messages will be an innovation.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Brownsville+Herald&rft.atitle=Army+Adopts+24-Hour+Clock+Plan&rft.pages=2&rft.date=1942-06-26&rft_id=https%3A%2F%2Fnewspaperarchive.com%2Fus%2Ftexas%2Fbrownsville%2Fbrownsville-herald%2F1942%2F06-26%2Fpage-2%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-ElPaso1942-26"><span class="mw-cite-backlink"><b><a href="#cite_ref-ElPaso1942_26-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite class="citation news cs1"><a rel="nofollow" class="external text" href="https://newspaperarchive.com/us/texas/el-paso/el-paso-herald-post/1942/07-03/page-3/">"It Will Be 2100 O'Clock at Ft. Bliss At 3 p. m."</a> <i>El Paso Herald-Post</i>. <a href="/wiki/El_Paso" class="mw-redirect" title="El Paso">El Paso</a>. 3 July 1942. p. 3. <q>The Army has a new time system — Greenwich Civil Time — to be used in radiograms, telegrams, and all official communications. [...] Effective 10 p. m. Monday, the War Department adopted the 24-hour system, which is used internationally with the Navy and the Armed forces of associated nations. [...] the six hours difference between Mountain War Time and actual Greenwich time must be taken into account, so that 12 noon is expressed on communications as 1800.</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=El+Paso+Herald-Post&rft.atitle=It+Will+Be+2100+O%27Clock+at+Ft.+Bliss+At+3+p.+m.&rft.pages=3&rft.date=1942-07-03&rft_id=https%3A%2F%2Fnewspaperarchive.com%2Fus%2Ftexas%2Fel-paso%2Fel-paso-herald-post%2F1942%2F07-03%2Fpage-3%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span></span> </li> <li id="cite_note-counting-time-27"><span class="mw-cite-backlink">^ <a href="#cite_ref-counting-time_27-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-counting-time_27-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-counting-time_27-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-counting-time_27-3"><sup><i><b>d</b></i></sup></a></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBoardman2011" class="citation book cs1">Boardman, Peter (July 2011). <a rel="nofollow" class="external text" href="http://clock24.nfshost.com/counting-time.html"><i>Counting Time: a brief history of the 24-hour clock</i></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Counting+Time%3A+a+brief+history+of+the+24-hour+clock&rft.date=2011-07&rft.aulast=Boardman&rft.aufirst=Peter&rft_id=http%3A%2F%2Fclock24.nfshost.com%2Fcounting-time.html&rfr_id=info%3Asid%2Fen.wikipedia.org%3A24-hour+clock" class="Z3988"></span><sup class="noprint Inline-Template" style="white-space:nowrap;">[<i><a href="/wiki/Wikipedia:Verifiability#Self-published_sources" title="Wikipedia:Verifiability"><span title="This reference citation appears to be to a self-published source. (September 2014)">self-published source</span></a></i>]</sup></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">Sarasota Herald-Tribune 1943 May 14.</span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=24-hour_clock&action=edit&section=10" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px solid #aaa;font-size:88%;line-height:1.25em;background-color:var(--background-color-interactive-subtle,#f8f9fa);display:flow-root}.mw-parser-output .side-box-abovebelow,.mw-parser-output .side-box-text{padding:0.25em 0.9em}.mw-parser-output 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href="https://commons.wikimedia.org/wiki/Category:24-hour_clocks" class="extiw" title="commons:Category:24-hour clocks">24-hour clocks</a></span>.</div></div> </div> <ul><li><a rel="nofollow" class="external text" href="http://clock24.nfshost.com/counting-time.html"><i>Counting Time: a brief history of the 24-hour clock</i> (free e-book)</a></li></ul> <div class="navbox-styles"><style data-mw-deduplicate="TemplateStyles:r1129693374">.mw-parser-output .hlist dl,.mw-parser-output .hlist ol,.mw-parser-output .hlist ul{margin:0;padding:0}.mw-parser-output .hlist dd,.mw-parser-output .hlist dt,.mw-parser-output .hlist li{margin:0;display:inline}.mw-parser-output .hlist.inline,.mw-parser-output .hlist.inline dl,.mw-parser-output .hlist.inline ol,.mw-parser-output .hlist.inline ul,.mw-parser-output .hlist dl dl,.mw-parser-output .hlist dl ol,.mw-parser-output .hlist dl ul,.mw-parser-output .hlist ol dl,.mw-parser-output .hlist ol ol,.mw-parser-output .hlist ol ul,.mw-parser-output .hlist ul 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href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"></div><div role="navigation" class="navbox" aria-labelledby="Time" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="2"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><style data-mw-deduplicate="TemplateStyles:r1239400231">.mw-parser-output .navbar{display:inline;font-size:88%;font-weight:normal}.mw-parser-output .navbar-collapse{float:left;text-align:left}.mw-parser-output .navbar-boxtext{word-spacing:0}.mw-parser-output .navbar ul{display:inline-block;white-space:nowrap;line-height:inherit}.mw-parser-output .navbar-brackets::before{margin-right:-0.125em;content:"[ "}.mw-parser-output .navbar-brackets::after{margin-left:-0.125em;content:" ]"}.mw-parser-output .navbar li{word-spacing:-0.125em}.mw-parser-output .navbar a>span,.mw-parser-output .navbar a>abbr{text-decoration:inherit}.mw-parser-output .navbar-mini abbr{font-variant:small-caps;border-bottom:none;text-decoration:none;cursor:inherit}.mw-parser-output .navbar-ct-full{font-size:114%;margin:0 7em}.mw-parser-output .navbar-ct-mini{font-size:114%;margin:0 4em}html.skin-theme-clientpref-night .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}@media(prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .navbar li a abbr{color:var(--color-base)!important}}@media print{.mw-parser-output .navbar{display:none!important}}</style><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Time_topics" title="Template:Time topics"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Time_topics" title="Template talk:Time topics"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Time_topics" title="Special:EditPage/Template:Time topics"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Time" style="font-size:114%;margin:0 4em"><a href="/wiki/Time" title="Time">Time</a></div></th></tr><tr><th scope="row" class="navbox-group" style="width:1%">Key concepts</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Past" title="Past">Past</a></li> <li><a href="/wiki/Present" title="Present">Present</a></li> <li><a href="/wiki/Future" title="Future">Future</a></li> <li><a href="/wiki/Eternity" title="Eternity">Eternity</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Horology" class="mw-redirect" title="Horology">Measurement</a><br />and <a href="/wiki/Time_standard" title="Time standard">standards</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Chronometry" title="Chronometry">Chronometry</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">UTC</a></li> <li><a href="/wiki/Universal_Time" title="Universal Time">UT</a></li> <li><a href="/wiki/International_Atomic_Time" title="International Atomic Time">TAI</a></li> <li><a href="/wiki/Unit_of_time" title="Unit of time">Unit of time</a></li> <li><a href="/wiki/Orders_of_magnitude_(time)" title="Orders of magnitude (time)">Orders of magnitude (time)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/System_of_measurement" class="mw-redirect" title="System of measurement">Measurement<br />systems</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Italian_six-hour_clock" title="Italian six-hour clock">Italian six-hour clock</a></li> <li><a href="/wiki/Thai_six-hour_clock" title="Thai six-hour clock">Thai six-hour clock</a></li> <li><a href="/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a></li> <li><a class="mw-selflink selflink">24-hour clock</a></li> <li><a href="/wiki/Relative_hour" title="Relative hour">Relative hour</a></li> <li><a href="/wiki/Daylight_saving_time" title="Daylight saving time">Daylight saving time</a></li> <li><a href="/wiki/Traditional_Chinese_timekeeping" title="Traditional Chinese timekeeping">Chinese</a></li> <li><a href="/wiki/Decimal_time" title="Decimal time">Decimal</a></li> <li><a href="/wiki/Hexadecimal_time" title="Hexadecimal time">Hexadecimal</a></li> <li><a href="/wiki/Hindu_units_of_time" title="Hindu units of time">Hindu</a></li> <li><a href="/wiki/Metric_time" title="Metric time">Metric</a></li> <li><a href="/wiki/Roman_timekeeping" title="Roman timekeeping">Roman</a></li> <li><a href="/wiki/Sidereal_time" title="Sidereal time">Sidereal</a></li> <li><a href="/wiki/Solar_time" title="Solar time">Solar</a></li> <li><a href="/wiki/Time_zone" title="Time zone">Time zone</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Calendar" title="Calendar">Calendars</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Calendar#Systems" title="Calendar">Main types</a> <ul><li><a href="/wiki/Solar_calendar" title="Solar calendar">Solar</a></li> <li><a href="/wiki/Lunar_calendar" title="Lunar calendar">Lunar</a></li> <li><a href="/wiki/Lunisolar_calendar" title="Lunisolar calendar">Lunisolar</a></li></ul></li> <li><a href="/wiki/Gregorian_calendar" title="Gregorian calendar">Gregorian</a></li> <li><a href="/wiki/Julian_calendar" title="Julian calendar">Julian</a></li> <li><a href="/wiki/Hebrew_calendar" title="Hebrew calendar">Hebrew</a></li> <li><a href="/wiki/Islamic_calendar" title="Islamic calendar">Islamic</a></li> <li><a href="/wiki/Solar_Hijri_calendar" title="Solar Hijri calendar">Solar Hijri</a></li> <li><a href="/wiki/Chinese_calendar" title="Chinese calendar">Chinese</a></li> <li><a href="/wiki/Hindu_calendar" title="Hindu calendar">Hindu Panchang</a></li> <li><a href="/wiki/Maya_calendar" title="Maya calendar">Maya</a></li> <li><i><a href="/wiki/List_of_calendars" title="List of calendars">List</a></i></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Clock" title="Clock">Clocks</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Clock#Types" title="Clock">Main types</a> <ul><li><a href="/wiki/Astronomical_clock" title="Astronomical clock">astronomical</a> <ul><li><a href="/wiki/Astrarium" title="Astrarium">astrarium</a></li></ul></li> <li><a href="/wiki/Atomic_clock" title="Atomic clock">atomic</a> <ul><li><a href="/wiki/Quantum_clock" class="mw-redirect" title="Quantum clock">quantum</a></li></ul></li> <li><a href="/wiki/Hourglass" title="Hourglass">hourglass</a></li> <li><a href="/wiki/Marine_chronometer" title="Marine chronometer">marine</a></li> <li><a href="/wiki/Sundial" title="Sundial">sundial</a></li> <li><a href="/wiki/Watch" title="Watch">watch</a> <ul><li><a href="/wiki/Mechanical_watch" title="Mechanical watch">mechanical</a></li> <li><a href="/wiki/Stopwatch" title="Stopwatch">stopwatch</a></li></ul></li> <li><a href="/wiki/Water_clock" title="Water clock">water-based</a></li></ul></li> <li><a href="/wiki/Cuckoo_clock" title="Cuckoo clock">Cuckoo clock</a></li> <li><a href="/wiki/Digital_clock" title="Digital clock">Digital clock</a></li> <li><a href="/wiki/Grandfather_clock" title="Grandfather clock">Grandfather clock</a></li> <li><i><a href="/wiki/History_of_timekeeping_devices" title="History of timekeeping devices">History</a></i> <ul><li><i><a href="/wiki/Timeline_of_time_measurement_inventions" title="Timeline of time measurement inventions">Timeline</a></i></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><div class="hlist"><ul><li><a href="/wiki/Chronology" title="Chronology">Chronology</a></li><li><a href="/wiki/History" title="History">History</a></li></ul></div></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Astronomical_chronology" title="Astronomical chronology">Astronomical chronology</a></li> <li><a href="/wiki/Big_History" title="Big History">Big History</a></li> <li><a href="/wiki/Calendar_era" title="Calendar era">Calendar era</a></li> <li><a href="/wiki/Deep_time" title="Deep time">Deep time</a></li> <li><a href="/wiki/Periodization" title="Periodization">Periodization</a></li> <li><a href="/wiki/Regnal_year" title="Regnal year">Regnal year</a></li> <li><a href="/wiki/Timeline" title="Timeline">Timeline</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Philosophy_of_space_and_time" title="Philosophy of space and time">Philosophy of time</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/A_series_and_B_series" title="A series and B series">A series and B series</a></li> <li><a href="/wiki/B-theory_of_time" title="B-theory of time">B-theory of time</a></li> <li><a href="/wiki/Chronocentrism" title="Chronocentrism">Chronocentrism</a></li> <li><a href="/wiki/Duration_(philosophy)" title="Duration (philosophy)">Duration</a></li> <li><a href="/wiki/Endurantism" title="Endurantism">Endurantism</a></li> <li><a href="/wiki/Eternal_return" title="Eternal return">Eternal return</a></li> <li><a href="/wiki/Eternalism_(philosophy_of_time)" title="Eternalism (philosophy of time)">Eternalism</a></li> <li><a href="/wiki/Event_(philosophy)" title="Event (philosophy)">Event</a></li> <li><a href="/wiki/Perdurantism" title="Perdurantism">Perdurantism</a></li> <li><a href="/wiki/Philosophical_presentism" title="Philosophical presentism">Presentism</a></li> <li><a href="/wiki/Temporal_finitism" title="Temporal finitism">Temporal finitism</a></li> <li><a href="/wiki/Temporal_parts" title="Temporal parts">Temporal parts</a></li> <li><i><a href="/wiki/The_Unreality_of_Time" title="The Unreality of Time">The Unreality of Time</a></i></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><div class="hlist"><ul><li><a href="/wiki/Category:Time_in_religion" title="Category:Time in religion">Religion</a></li><li><a href="/wiki/Template:Time_in_religion_and_mythology" title="Template:Time in religion and mythology">Mythology</a></li></ul></div></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ages_of_Man" title="Ages of Man">Ages of Man</a></li> <li><a href="/wiki/Destiny" title="Destiny">Destiny</a></li> <li><a href="/wiki/Immortality" title="Immortality">Immortality</a></li> <li><a href="/wiki/The_Dreaming" title="The Dreaming">Dreamtime</a></li> <li><a href="/wiki/K%C4%81la" title="Kāla">Kāla</a></li> <li><a href="/wiki/Time_and_fate_deities" title="Time and fate deities">Time and fate deities</a> <ul><li><a href="/wiki/Father_Time" title="Father Time">Father Time</a></li></ul></li> <li><a href="/wiki/Wheel_of_time" title="Wheel of time">Wheel of time</a> <ul><li><a href="/wiki/Kalachakra" title="Kalachakra">Kalachakra</a></li></ul></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Time_perception" title="Time perception">Human experience</a><br />and <a href="/wiki/Time-use_research" title="Time-use research">use of time</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chronemics" title="Chronemics">Chronemics</a></li> <li><a href="/wiki/Generation_time" title="Generation time">Generation time</a></li> <li><a href="/wiki/Mental_chronometry" title="Mental chronometry">Mental chronometry</a></li> <li><a href="/wiki/Duration_(music)" title="Duration (music)">Music</a> <ul><li><a href="/wiki/Tempo" title="Tempo">tempo</a></li> <li><a href="/wiki/Time_signature" title="Time signature">time signature</a></li></ul></li> <li><a href="/wiki/Rosy_retrospection" title="Rosy retrospection">Rosy retrospection</a></li> <li><a href="/wiki/Tense%E2%80%93aspect%E2%80%93mood" title="Tense–aspect–mood">Tense–aspect–mood</a></li> <li><a href="/wiki/Time_management" title="Time management">Time management</a></li> <li><a href="/wiki/Yesterday_(time)" title="Yesterday (time)">Yesterday</a> – <a href="/wiki/Present" title="Present">Today</a> – <a href="/wiki/Tomorrow_(time)" title="Tomorrow (time)">Tomorrow</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Time in <a href="/wiki/Science" title="Science">science</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Geology" title="Geology">Geology</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Geologic_time_scale" title="Geologic time scale">Geological time</a> <ul><li><a href="/wiki/Age_(geology)" class="mw-redirect" title="Age (geology)">age</a></li> <li><a href="/wiki/Chronozone" title="Chronozone">chron</a></li> <li><a href="/wiki/Eon_(geology)" class="mw-redirect" title="Eon (geology)">eon</a></li> <li><a href="/wiki/Epoch_(geology)" class="mw-redirect" title="Epoch (geology)">epoch</a></li> <li><a href="/wiki/Era_(geology)" class="mw-redirect" title="Era (geology)">era</a></li> <li><a href="/wiki/Geological_period" class="mw-redirect" title="Geological period">period</a></li></ul></li> <li><a href="/wiki/Geochronology" title="Geochronology">Geochronology</a></li> <li><a href="/wiki/Geological_history_of_Earth" title="Geological history of Earth">Geological history of Earth</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;"><a href="/wiki/Time_in_physics" title="Time in physics">Physics</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Absolute_space_and_time" title="Absolute space and time">Absolute space and time</a></li> <li><a href="/wiki/Arrow_of_time" title="Arrow of time">Arrow of time</a></li> <li><a href="/wiki/Chronon" title="Chronon">Chronon</a></li> <li><a href="/wiki/Coordinate_time" title="Coordinate time">Coordinate time</a></li> <li><a href="/wiki/Instant" title="Instant">Instant</a></li> <li><a href="/wiki/Proper_time" title="Proper time">Proper time</a></li> <li><a href="/wiki/Spacetime" title="Spacetime">Spacetime</a></li> <li><a href="/wiki/Theory_of_relativity" title="Theory of relativity">Theory of relativity</a></li> <li><a href="/wiki/Time_domain" title="Time domain">Time domain</a></li> <li><a href="/wiki/Time_translation_symmetry" class="mw-redirect" title="Time translation symmetry">Time translation symmetry</a></li> <li><a href="/wiki/T-symmetry" title="T-symmetry">Time reversal symmetry</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:6.5em;font-weight:normal; text-align:center;">Other fields</th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chronological_dating" title="Chronological dating">Chronological dating</a></li> <li><a href="/wiki/Chronobiology" title="Chronobiology">Chronobiology</a> <ul><li><a href="/wiki/Circadian_rhythm" title="Circadian rhythm">Circadian rhythms</a></li></ul></li> <li><a href="/wiki/Chemical_clock" title="Chemical clock">Clock reaction</a></li> <li><a href="/wiki/Glottochronology" title="Glottochronology">Glottochronology</a></li> <li><a href="/wiki/Time_geography" title="Time geography">Time geography</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Leap_year" title="Leap year">Leap year</a></li> <li><a href="/wiki/Memory" title="Memory">Memory</a></li> <li><a href="/wiki/Moment_(unit)" title="Moment (unit)">Moment</a></li> <li><a href="/wiki/Space" title="Space">Space</a></li> <li><a href="/wiki/System_time" title="System time">System time</a></li> <li><i><a href="/wiki/Tempus_fugit" title="Tempus fugit">Tempus fugit</a></i></li> <li><a href="/wiki/Time_capsule" title="Time capsule">Time capsule</a></li> <li><a href="/wiki/Time_immemorial" title="Time immemorial">Time immemorial</a></li> <li><a href="/wiki/Time_travel" title="Time travel">Time travel</a></li></ul> </div></td></tr><tr><td class="navbox-abovebelow" colspan="2"><div> <ul><li><span class="noviewer" typeof="mw:File"><span title="Category"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/16px-Symbol_category_class.svg.png" decoding="async" width="16" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/23px-Symbol_category_class.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/96/Symbol_category_class.svg/31px-Symbol_category_class.svg.png 2x" data-file-width="180" data-file-height="185" /></span></span> <a href="/wiki/Category:Time" title="Category:Time">Category</a></li> <li><span class="noviewer" typeof="mw:File"><span title="Commons page"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png" decoding="async" width="12" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/24px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></span></span> <a href="https://commons.wikimedia.org/wiki/Category:Time" class="extiw" title="commons:Category:Time">Commons</a></li></ul> </div></td></tr></tbody></table></div> <div class="navbox-styles"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236075235"></div><div role="navigation" class="navbox" aria-labelledby="Time_measurement_and_standards" style="padding:3px"><table class="nowraplinks hlist mw-collapsible autocollapse navbox-inner" style="border-spacing:0;background:transparent;color:inherit"><tbody><tr><th scope="col" class="navbox-title" colspan="3"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1129693374"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239400231"><div class="navbar plainlinks hlist navbar-mini"><ul><li class="nv-view"><a href="/wiki/Template:Time_measurement_and_standards" title="Template:Time measurement and standards"><abbr title="View this template">v</abbr></a></li><li class="nv-talk"><a href="/wiki/Template_talk:Time_measurement_and_standards" title="Template talk:Time measurement and standards"><abbr title="Discuss this template">t</abbr></a></li><li class="nv-edit"><a href="/wiki/Special:EditPage/Template:Time_measurement_and_standards" title="Special:EditPage/Template:Time measurement and standards"><abbr title="Edit this template">e</abbr></a></li></ul></div><div id="Time_measurement_and_standards" style="font-size:114%;margin:0 4em"><a href="/wiki/Time" title="Time">Time measurement</a> and <a href="/wiki/Time_standard" title="Time standard">standards</a></div></th></tr><tr><td class="navbox-abovebelow" colspan="3"><div> <ul><li><a href="/wiki/Chronometry" title="Chronometry">Chronometry</a></li> <li><a href="/wiki/Orders_of_magnitude_(time)" title="Orders of magnitude (time)">Orders of magnitude</a></li> <li><a href="/wiki/Time_metrology" class="mw-redirect" title="Time metrology">Metrology</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">International standards</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Coordinated_Universal_Time" title="Coordinated Universal Time">Coordinated Universal Time</a> <ul><li><a href="/wiki/UTC_offset" title="UTC offset">offset</a></li></ul></li> <li><a href="/wiki/Universal_Time" title="Universal Time">UT</a></li> <li><a href="/wiki/%CE%94T_(timekeeping)" title="ΔT (timekeeping)">ΔT</a></li> <li><a href="/wiki/DUT1" title="DUT1">DUT1</a></li> <li><a href="/wiki/International_Earth_Rotation_and_Reference_Systems_Service" title="International Earth Rotation and Reference Systems Service">International Earth Rotation and Reference Systems Service</a></li> <li><a href="/wiki/ISO_31-1" title="ISO 31-1">ISO 31-1</a></li> <li><a href="/wiki/ISO_8601" title="ISO 8601">ISO 8601</a></li> <li><a href="/wiki/International_Atomic_Time" title="International Atomic Time">International Atomic Time</a></li> <li><a href="/wiki/12-hour_clock" title="12-hour clock">12-hour clock</a></li> <li><a class="mw-selflink selflink">24-hour clock</a></li> <li><a href="/wiki/Barycentric_Coordinate_Time" title="Barycentric Coordinate Time">Barycentric Coordinate Time</a></li> <li><a href="/wiki/Barycentric_Dynamical_Time" title="Barycentric Dynamical Time">Barycentric Dynamical Time</a></li> <li><a href="/wiki/Civil_time" title="Civil time">Civil time</a></li> <li><a href="/wiki/Daylight_saving_time" title="Daylight saving time">Daylight saving time</a></li> <li><a href="/wiki/Geocentric_Coordinate_Time" title="Geocentric Coordinate Time">Geocentric Coordinate Time</a></li> <li><a href="/wiki/International_Date_Line" title="International Date Line">International Date Line</a></li> <li><a href="/wiki/IERS_Reference_Meridian" title="IERS Reference Meridian">IERS Reference Meridian</a></li> <li><a href="/wiki/Leap_second" title="Leap second">Leap second</a></li> <li><a href="/wiki/Solar_time" title="Solar time">Solar time</a></li> <li><a href="/wiki/Terrestrial_Time" title="Terrestrial Time">Terrestrial Time</a></li> <li><a href="/wiki/Time_zone" title="Time zone">Time zone</a></li> <li><a href="/wiki/180th_meridian" title="180th meridian">180th meridian</a></li></ul> </div></td><td class="noviewer navbox-image" rowspan="9" style="width:1px;padding:0 0 0 2px"><div><span typeof="mw:File"><a href="/wiki/Hourglass" title="Hourglass"><img alt="template illustration" src="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Marine_sandglass_MMM.jpg/75px-Marine_sandglass_MMM.jpg" decoding="async" width="75" height="175" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Marine_sandglass_MMM.jpg/113px-Marine_sandglass_MMM.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/70/Marine_sandglass_MMM.jpg/150px-Marine_sandglass_MMM.jpg 2x" data-file-width="1637" data-file-height="3819" /></a></span><br /><span typeof="mw:File"><a href="/wiki/Time_zone" title="Time zone"><img alt="template illustration" src="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png/75px-Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png" decoding="async" width="75" height="152" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/6/63/Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png/113px-Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/6/63/Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png/150px-Aleutian_Islands_with_180th_meridian_and_International_Date_Line_%28cropped%29.png 2x" data-file-width="496" data-file-height="1007" /></a></span></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Obsolete standards</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Ephemeris_time" title="Ephemeris time">Ephemeris time</a></li> <li><a href="/wiki/Greenwich_Mean_Time" title="Greenwich Mean Time">Greenwich Mean Time</a></li> <li><a href="/wiki/Prime_meridian" title="Prime meridian">Prime meridian</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Time_in_physics" title="Time in physics">Time in physics</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Absolute_space_and_time" title="Absolute space and time">Absolute space and time</a></li> <li><a href="/wiki/Spacetime" title="Spacetime">Spacetime</a></li> <li><a href="/wiki/Chronon" title="Chronon">Chronon</a></li> <li><a href="/wiki/Continuous_signal" class="mw-redirect" title="Continuous signal">Continuous signal</a></li> <li><a href="/wiki/Coordinate_time" title="Coordinate time">Coordinate time</a></li> <li><a href="/wiki/Cosmological_decade" title="Cosmological decade">Cosmological decade</a></li> <li><a href="/wiki/Discrete_time_and_continuous_time" title="Discrete time and continuous time">Discrete time and continuous time</a></li> <li><a href="/wiki/Proper_time" title="Proper time">Proper time</a></li> <li><a href="/wiki/Theory_of_relativity" title="Theory of relativity">Theory of relativity</a></li> <li><a href="/wiki/Time_dilation" title="Time dilation">Time dilation</a></li> <li><a href="/wiki/Gravitational_time_dilation" title="Gravitational time dilation">Gravitational time dilation</a></li> <li><a href="/wiki/Time_domain" title="Time domain">Time domain</a></li> <li><a href="/wiki/Time-translation_symmetry" title="Time-translation symmetry">Time-translation symmetry</a></li> <li><a href="/wiki/T-symmetry" title="T-symmetry">T-symmetry</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Horology" class="mw-redirect" title="Horology">Horology</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Clock" title="Clock">Clock</a></li> <li><a href="/wiki/Astrarium" title="Astrarium">Astrarium</a></li> <li><a href="/wiki/Atomic_clock" title="Atomic clock">Atomic clock</a></li> <li><a href="/wiki/Complication_(horology)" title="Complication (horology)">Complication</a></li> <li><a href="/wiki/History_of_timekeeping_devices" title="History of timekeeping devices">History of timekeeping devices</a></li> <li><a href="/wiki/Hourglass" title="Hourglass">Hourglass</a></li> <li><a href="/wiki/Marine_chronometer" title="Marine chronometer">Marine chronometer</a></li> <li><a href="/wiki/Marine_sandglass" title="Marine sandglass">Marine sandglass</a></li> <li><a href="/wiki/Radio_clock" title="Radio clock">Radio clock</a></li> <li><a href="/wiki/Watch" title="Watch">Watch</a> <ul><li><a href="/wiki/Stopwatch" title="Stopwatch">stopwatch</a></li></ul></li> <li><a href="/wiki/Water_clock" title="Water clock">Water clock</a></li> <li><a href="/wiki/Sundial" title="Sundial">Sundial</a></li> <li><a href="/wiki/Dialing_scales" title="Dialing scales">Dialing scales</a></li> <li><a href="/wiki/Equation_of_time" title="Equation of time">Equation of time</a></li> <li><a href="/wiki/History_of_sundials" title="History of sundials">History of sundials</a></li> <li><a href="/wiki/Schema_for_horizontal_dials" title="Schema for horizontal dials">Sundial markup schema</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Calendar" title="Calendar">Calendar</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Gregorian_calendar" title="Gregorian calendar">Gregorian</a></li> <li><a href="/wiki/Hebrew_calendar" title="Hebrew calendar">Hebrew</a></li> <li><a href="/wiki/Hindu_calendar" title="Hindu calendar">Hindu</a></li> <li><a href="/wiki/Holocene_calendar" title="Holocene calendar">Holocene</a></li> <li><a href="/wiki/Islamic_calendar" title="Islamic calendar">Islamic</a> (lunar Hijri)</li> <li><a href="/wiki/Julian_calendar" title="Julian calendar">Julian</a></li> <li><a href="/wiki/Solar_Hijri_calendar" title="Solar Hijri calendar">Solar Hijri</a></li> <li><a href="/wiki/Astronomical_year_numbering" title="Astronomical year numbering">Astronomical</a></li> <li><a href="/wiki/Dominical_letter" title="Dominical letter">Dominical letter</a></li> <li><a href="/wiki/Epact" title="Epact">Epact</a></li> <li><a href="/wiki/Equinox" title="Equinox">Equinox</a></li> <li><a href="/wiki/Intercalation_(timekeeping)" title="Intercalation (timekeeping)">Intercalation</a></li> <li><a href="/wiki/Julian_day" title="Julian day">Julian day</a></li> <li><a href="/wiki/Leap_year" title="Leap year">Leap year</a></li> <li><a href="/wiki/Lunar_calendar" title="Lunar calendar">Lunar</a></li> <li><a href="/wiki/Lunisolar_calendar" title="Lunisolar calendar">Lunisolar</a></li> <li><a href="/wiki/Solar_calendar" title="Solar calendar">Solar</a></li> <li><a href="/wiki/Solstice" title="Solstice">Solstice</a></li> <li><a href="/wiki/Tropical_year" title="Tropical year">Tropical year</a></li> <li><a href="/wiki/Determination_of_the_day_of_the_week" title="Determination of the day of the week">Weekday determination</a></li> <li><a href="/wiki/Names_of_the_days_of_the_week" title="Names of the days of the week">Weekday names</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Archaeology and geology</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chronological_dating" title="Chronological dating">Chronological dating</a></li> <li><a href="/wiki/Geologic_time_scale" title="Geologic time scale">Geologic time scale</a></li> <li><a href="/wiki/International_Commission_on_Stratigraphy" title="International Commission on Stratigraphy">International Commission on Stratigraphy</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%"><a href="/wiki/Astronomical_chronology" title="Astronomical chronology">Astronomical chronology</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Galactic_year" title="Galactic year">Galactic year</a></li> <li><a href="/wiki/Nuclear_timescale" title="Nuclear timescale">Nuclear timescale</a></li> <li><a href="/wiki/Precession" title="Precession">Precession</a></li> <li><a href="/wiki/Sidereal_time" title="Sidereal time">Sidereal time</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Other <a href="/wiki/Unit_of_time" title="Unit of time">units of time</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Instant" title="Instant">Instant</a></li> <li><a href="/wiki/Flick_(time)" title="Flick (time)">Flick</a></li> <li><a href="/wiki/Shake_(unit)" title="Shake (unit)">Shake</a></li> <li><a href="/wiki/Jiffy_(time)" title="Jiffy (time)">Jiffy</a></li> <li><a href="/wiki/Second" title="Second">Second</a></li> <li><a href="/wiki/Minute" title="Minute">Minute</a></li> <li><a href="/wiki/Moment_(unit)" title="Moment (unit)">Moment</a></li> <li><a href="/wiki/Hour" title="Hour">Hour</a></li> <li><a href="/wiki/Day" title="Day">Day</a></li> <li><a href="/wiki/Week" title="Week">Week</a></li> <li><a href="/wiki/Fortnight" title="Fortnight">Fortnight</a></li> <li><a href="/wiki/Month" title="Month">Month</a></li> <li><a href="/wiki/Year" title="Year">Year</a></li> <li><a href="/wiki/Olympiad" title="Olympiad">Olympiad</a></li> <li><a href="/wiki/Lustrum" title="Lustrum">Lustrum</a></li> <li><a href="/wiki/Decade" title="Decade">Decade</a></li> <li><a href="/wiki/Century" title="Century">Century</a></li> <li><a href="/wiki/Saeculum" title="Saeculum">Saeculum</a></li> <li><a href="/wiki/Millennium" title="Millennium">Millennium</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%">Related topics</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Chronology" title="Chronology">Chronology</a></li> <li><a href="/wiki/Duration_(philosophy)" title="Duration (philosophy)">Duration</a> <ul><li><a href="/wiki/Duration_(music)" title="Duration (music)">music</a></li></ul></li> <li><a href="/wiki/Mental_chronometry" title="Mental chronometry">Mental chronometry</a></li> <li><a href="/wiki/Decimal_time" title="Decimal time">Decimal time</a></li> <li><a href="/wiki/Metric_time" title="Metric time">Metric time</a></li> <li><a href="/wiki/System_time" title="System time">System time</a></li> <li><a href="/wiki/Time_metrology" class="mw-redirect" title="Time metrology">Time metrology</a></li> <li><a href="/wiki/Time_value_of_money" title="Time value of money">Time value of money</a></li> <li><a href="/wiki/Timekeeper" title="Timekeeper">Timekeeper</a></li></ul> </div></td></tr></tbody></table></div>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" width="1" height="1" style="border: none; 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