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<span>Watch</span> </a> </li> <li id="page-actions-edit" class="page-actions-menu__list-item"> <a role="button" id="ca-edit" href="/w/index.php?title=Julian_year_(astronomy)&action=edit" data-event-name="menu.edit" data-mw="interface" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet edit-page menu__item--page-actions-edit"> <span class="minerva-icon minerva-icon--edit"></span> <span>Edit</span> </a> </li> </ul> </nav>  <div id="mw-content-subtitle"></div> </div> <div id="bodyContent" class="content"> <div id="mw-content-text" class="mw-body-content"><script>function mfTempOpenSection(id){var block=document.getElementById("mf-section-"+id);block.className+=" open-block";block.previousSibling.className+=" open-block";}</script><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><section class="mf-section-0" id="mf-section-0"> <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">This article is about the time interval used in astronomy. For years in the Julian calendar, see <a href="/wiki/Julian_calendar" title="Julian calendar">Julian calendar</a>.</div> <p>In <a href="/wiki/Astronomy" title="Astronomy">astronomy</a>, a <b>Julian year</b> (symbol: <b>a</b> or <b>a<sub>j</sub></b>) is a <a href="/wiki/Units_of_measurement" class="mw-redirect" title="Units of measurement">unit of measurement</a> of <a href="/wiki/Time" title="Time">time</a> defined as exactly 365.25 <a href="/wiki/Day" title="Day">days</a> of <span class="nowrap"><span data-sort-value="7004864000000000000♠"></span>86<span style="margin-left:.25em;">400</span></span> <a href="/wiki/SI" class="mw-redirect" title="SI">SI</a> <a href="/wiki/Second" title="Second">seconds</a> each.<sup id="cite_ref-explanatory_1-0" class="reference"><a href="#cite_note-explanatory-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-units_2-0" class="reference"><a href="#cite_note-units-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-IAU_3-0" class="reference"><a href="#cite_note-IAU-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The length of the Julian year is the average length of the <a href="/wiki/Year" title="Year">year</a> in the <a href="/wiki/Julian_calendar" title="Julian calendar">Julian calendar</a> that was used in Western societies <a href="/wiki/Adoption_of_the_Gregorian_calendar" title="Adoption of the Gregorian calendar">until the adoption of the Gregorian Calendar</a>, and from which the unit is named. Nevertheless, because astronomical Julian years are measuring duration rather than designating dates, this Julian year does not correspond to years in the Julian calendar or any other calendar. Nor does it correspond to the many other ways of defining a year. </p> <div id="toc" class="toc" role="navigation" aria-labelledby="mw-toc-heading"><input type="checkbox" role="button" id="toctogglecheckbox" class="toctogglecheckbox" style="display:none"><div class="toctitle" lang="en" dir="ltr"><h2 id="mw-toc-heading">Contents</h2><span class="toctogglespan"><label class="toctogglelabel" for="toctogglecheckbox"></label></span></div> <ul> <li class="toclevel-1 tocsection-1"><a href="#Usage"><span class="tocnumber">1</span> <span class="toctext">Usage</span></a></li> <li class="toclevel-1 tocsection-2"><a href="#Epochs"><span class="tocnumber">2</span> <span class="toctext">Epochs</span></a></li> <li class="toclevel-1 tocsection-3"><a href="#Julian_calendar_distinguished"><span class="tocnumber">3</span> <span class="toctext">Julian calendar distinguished</span></a></li> <li class="toclevel-1 tocsection-4"><a href="#Julian_day_distinguished"><span class="tocnumber">4</span> <span class="toctext">Julian day distinguished</span></a></li> <li class="toclevel-1 tocsection-5"><a href="#References"><span class="tocnumber">5</span> <span class="toctext">References</span></a></li> <li class="toclevel-1 tocsection-6"><a href="#External_links"><span class="tocnumber">6</span> <span class="toctext">External links</span></a></li> </ul> </div> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(1)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="Usage">Usage</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Julian_year_(astronomy)&action=edit&section=1" title="Edit section: Usage" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-1 collapsible-block" id="mf-section-1"> <p>The Julian year is not a unit of measurement in the <a href="/wiki/International_System_of_Units" title="International System of Units">International System of Units</a> (SI), but it is recognized by the <a href="/wiki/International_Astronomical_Union" title="International Astronomical Union">International Astronomical Union</a> (IAU) as a non-SI unit for use in astronomy.<sup id="cite_ref-IAU_3-1" class="reference"><a href="#cite_note-IAU-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> Before 1984, both the Julian year and the mean <a href="/wiki/Tropical_year" title="Tropical year">tropical year</a> were used by astronomers. In 1898, <a href="/wiki/Simon_Newcomb" title="Simon Newcomb">Simon Newcomb</a> used both in his <i><a href="/wiki/Newcomb%27s_Tables_of_the_Sun" title="Newcomb's Tables of the Sun">Tables of the Sun</a></i> in the form of the Julian century (36 525 days) and the "solar century" (<span class="nowrap"><span data-sort-value="7004365242200000000♠"></span>36<span style="margin-left:.25em;">524</span>.22</span> days), a rounded form of 100 mean <a href="/wiki/Tropical_year" title="Tropical year">tropical years</a> of <span class="nowrap"><span data-sort-value="7002365242198790000♠"></span>365.242<span style="margin-left:.25em;">198</span><span style="margin-left:.25em;">79</span></span> days each according to Newcomb.<sup id="cite_ref-Newcomb_5-0" class="reference"><a href="#cite_note-Newcomb-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> However, the mean tropical year is not suitable as a unit of measurement because it varies from year to year by a small amount, <span class="nowrap"><span data-sort-value="6992614000000000000♠"></span>6.14<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−8</sup></span> days according to Newcomb.<sup id="cite_ref-Newcomb_5-1" class="reference"><a href="#cite_note-Newcomb-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> In contrast, the Julian year is defined in terms of the SI unit one <a href="/wiki/Second" title="Second">second</a>, so is as accurate as that unit and is constant. It approximates both the <a href="/wiki/Sidereal_year" title="Sidereal year">sidereal year</a> and the tropical year to about ±0.008 days. The Julian year is the basis of the definition of the <a href="/wiki/Light-year" title="Light-year">light-year</a> as a unit of measurement of distance.<sup id="cite_ref-units_2-1" class="reference"><a href="#cite_note-units-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> </p> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(2)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="Epochs">Epochs</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Julian_year_(astronomy)&action=edit&section=2" title="Edit section: Epochs" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-2 collapsible-block" id="mf-section-2"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Epoch_(astronomy)" title="Epoch (astronomy)">Epoch (astronomy)</a></div> <p>In astronomy, an <i>epoch</i> specifies a precise moment in time. The positions of celestial objects and events, as measured from <a href="/wiki/Earth" title="Earth">Earth</a>, change over time, so when measuring or predicting celestial positions, the epoch to which they pertain must be specified. A new standard epoch is chosen about every 50 years. </p><p>The standard epoch in use today is <i>Julian epoch J2000.0</i>. It is exactly 12:00 <a href="/wiki/Terrestrial_Time" title="Terrestrial Time">TT</a> (close to but not exactly <a href="/wiki/Greenwich_Mean_Time" title="Greenwich Mean Time">Greenwich mean</a> noon) on <span class="nowrap">January 1, 2000</span> in the <a href="/wiki/Gregorian_calendar" title="Gregorian calendar">Gregorian</a> (<i>not</i> Julian) calendar. <i>Julian</i> within its name indicates that other Julian epochs can be a number of Julian years of 365.25 days each before or after J2000.0. For example, the future epoch J2100.0 will be exactly 36,525 days (one Julian century) from J2000.0 at 12:00 TT on <span class="nowrap">January 1, 2100</span> (the dates will still agree because the Gregorian century 2000–2100 will have the same number of days as a Julian century). </p><p>Because Julian years are not exactly the same length as years on the Gregorian calendar, astronomical epochs will diverge noticeably from the Gregorian calendar in a few hundred years. For example, in the next 1000 years, seven days will be dropped from the Gregorian calendar but not from 1000 Julian years, so J3000.0 will be <span class="nowrap">January 8, 3000 12:00 TT</span>. </p> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(3)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="Julian_calendar_distinguished">Julian calendar distinguished</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Julian_year_(astronomy)&action=edit&section=3" title="Edit section: Julian calendar distinguished" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-3 collapsible-block" id="mf-section-3"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Julian_calendar" title="Julian calendar">Julian calendar</a></div> <p>The <i>Julian year</i>, being a uniform measure of duration, should not be confused with the variable length historical years in the Julian calendar. An astronomical Julian year is never individually numbered. When not using <a href="/wiki/Julian_date" class="mw-redirect" title="Julian date">Julian day numbers</a> (<i>see next</i> §), astronomers follow the same conventional calendars that are accepted in the world community: They use the <a href="/wiki/Gregorian_calendar" title="Gregorian calendar">Gregorian calendar</a> for events since its introduction on <span class="nowrap">October 15, 1582</span> (or later, depending on country), and the Julian calendar for events before that date, and occasionally other, local calendars when appropriate for a given publication. </p> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(4)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="Julian_day_distinguished">Julian day distinguished</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Julian_year_(astronomy)&action=edit&section=4" title="Edit section: Julian day distinguished" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-4 collapsible-block" id="mf-section-4"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Julian_day" title="Julian day">Julian day</a></div> <p>A <i>Julian year</i> should not be confused with the <i>Julian day</i>, which is also used in astronomy (more properly called the <i>Julian day number</i> or <i>JDN</i>). The JDN uniquely specifies a place in time, without becoming bogged down in its date-in-month, week, month, or year in any particular calendar. Despite the similarity of names, there is almost no connection between the <i>Julian day numbers</i> and <i>Julian years</i>. </p><p>The Julian day number is a simplified time-keeping system originally intended to ease calculation with historical dates which involve a diversity of local, idiosyncratic calendars. It was adopted by astronomers in the mid-1800s, and identifies each <a href="/wiki/Calendar_date" title="Calendar date">date</a> as the integer number of days that have elapsed since a reference date (<a href="#Epochs">"epoch"</a>), chosen to precede most, if not all, historical records. A specific time within a day, always using <a href="/wiki/UTC" class="mw-redirect" title="UTC">UTC</a>, is specified via a decimal fraction. </p> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(5)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="References">References</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Julian_year_(astronomy)&action=edit&section=5" title="Edit section: References" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-5 collapsible-block" id="mf-section-5"> <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"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-explanatory-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-explanatory_1-0">^</a></b></span> <span class="reference-text">P. Kenneth Seidelmann, ed., <a rel="nofollow" class="external text" href="https://books.google.com/books/?id=uJ4JhGJANb4C&pg=PA696"><i>The explanatory supplement to the Astronomical Almanac</i></a>, (Mill Valley, Cal.: University Science Books, 1992), pp. 8, 696, 698–9, 704, 716, 730.</span> </li> <li id="cite_note-units-2"><span class="mw-cite-backlink">^ <a href="#cite_ref-units_2-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-units_2-1"><sup><i><b>b</b></i></sup></a></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 web cs1"><a rel="nofollow" class="external text" href="https://www.iau.org/publications/proceedings_rules/units/">"Measuring the Universe"</a>. <a href="/wiki/International_Astronomical_Union" title="International Astronomical Union">International Astronomical Union</a><span class="reference-accessdate">. Retrieved <span class="nowrap">March 22,</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=Measuring+the+Universe&rft.pub=International+Astronomical+Union&rft_id=https%3A%2F%2Fwww.iau.org%2Fpublications%2Fproceedings_rules%2Funits%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AJulian+year+%28astronomy%29" class="Z3988"></span></span> </li> <li id="cite_note-IAU-3"><span class="mw-cite-backlink">^ <a href="#cite_ref-IAU_3-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-IAU_3-1"><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="CITEREFInternational_Astronomical_Union" class="citation web cs1">International Astronomical Union. <a rel="nofollow" class="external text" href="https://web.archive.org/web/20070216041250/http://www.iau.org/Units.234.0.html">"Recommendations Concerning Units"</a>. Archived from <a rel="nofollow" class="external text" href="https://www.iau.org/publications/proceedings_rules/units/">the original</a> on February 16, 2007<span class="reference-accessdate">. Retrieved <span class="nowrap">February 18,</span> 2007</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Recommendations+Concerning+Units&rft.au=International+Astronomical+Union&rft_id=https%3A%2F%2Fwww.iau.org%2Fpublications%2Fproceedings_rules%2Funits%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AJulian+year+%28astronomy%29" class="Z3988"></span> Reprinted from the "IAU Style Manual" by G.A. Wilkinson, Comm. 5, in IAU Transactions XXB (1987).</span> </li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text">Harold Rabinowitz and Suzanne Vogel, <a rel="nofollow" class="external text" href="https://books.google.com/books?id=YZCqJzffR20C&pg=PA369"><i>The manual of scientific style</i></a> (Burlington, MA: Academic Press, 2009) 369.</span> </li> <li id="cite_note-Newcomb-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-Newcomb_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Newcomb_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text">Simon Newcomb, <a rel="nofollow" class="external text" href="https://archive.org/details/06AstronomicalPapersPreparedForTheUse"><i>Tables of the Four Inner Planets</i></a>, vol. 6 of <i>Astronomical Papers Prepared for the Use of the American Ephemeris and Nautical Almanac</i> (Washington, DC: 1898), pp. 10–11.</span> </li> </ol></div></div> </section><div class="mw-heading mw-heading2 section-heading" onclick="mfTempOpenSection(6)"><span class="indicator mf-icon mf-icon-expand mf-icon--small"></span><h2 id="External_links">External links</h2><span class="mw-editsection"> <a role="button" href="/w/index.php?title=Julian_year_(astronomy)&action=edit&section=6" title="Edit section: External links" class="cdx-button cdx-button--size-large cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--icon-only cdx-button--weight-quiet "> <span class="minerva-icon minerva-icon--edit"></span> <span>edit</span> </a> </span> </div><section class="mf-section-6 collapsible-block" id="mf-section-6"> <style data-mw-deduplicate="TemplateStyles:r1239009302">.mw-parser-output .portalbox{padding:0;margin:0.5em 0;display:table;box-sizing:border-box;max-width:175px;list-style:none}.mw-parser-output .portalborder{border:1px solid var(--border-color-base,#a2a9b1);padding:0.1em;background:var(--background-color-neutral-subtle,#f8f9fa)}.mw-parser-output .portalbox-entry{display:table-row;font-size:85%;line-height:110%;height:1.9em;font-style:italic;font-weight:bold}.mw-parser-output .portalbox-image{display:table-cell;padding:0.2em;vertical-align:middle;text-align:center}.mw-parser-output .portalbox-link{display:table-cell;padding:0.2em 0.2em 0.2em 0.3em;vertical-align:middle}@media(min-width:720px){.mw-parser-output .portalleft{clear:left;float:left;margin:0.5em 1em 0.5em 0}.mw-parser-output .portalright{clear:right;float:right;margin:0.5em 0 0.5em 1em}}</style><ul role="navigation" aria-label="Portals" class="noprint portalbox portalborder portalright"> <li class="portalbox-entry"><span class="portalbox-image"><span class="noviewer" typeof="mw:File"><span><noscript><img alt="" src="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/28px-Crab_Nebula.jpg" decoding="async" width="28" height="28" class="mw-file-element" data-file-width="3864" data-file-height="3864"></noscript><span class="lazy-image-placeholder" style="width: 28px;height: 28px;" data-src="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/28px-Crab_Nebula.jpg" data-alt="" data-width="28" data-height="28" data-srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/42px-Crab_Nebula.jpg 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/00/Crab_Nebula.jpg/56px-Crab_Nebula.jpg 2x" data-class="mw-file-element"> </span></span></span></span><span class="portalbox-link"><a href="/wiki/Portal:Astronomy" title="Portal:Astronomy">Astronomy portal</a></span></li></ul> <ul><li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFMichael_Allison_(@_Goddard_Institute_for_Space_Studies)2001" class="citation web cs1">Michael Allison (@ Goddard Institute for Space Studies) (2001). <a rel="nofollow" class="external text" href="https://web.archive.org/web/20110724121012/http://pweb.jps.net/~gangale3/other/allison2_frm.htm">"What is a "Year" (on Earth or Mars)?"</a>. <i>pweb.jps.net</i>. Archived from <a rel="nofollow" class="external text" href="http://pweb.jps.net/~gangale3/other/allison2_frm.htm">the original</a> on 2011-07-24<span class="reference-accessdate">. Retrieved <span class="nowrap">2011-07-26</span></span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=unknown&rft.jtitle=pweb.jps.net&rft.atitle=What+is+a+%22Year%22+%28on+Earth+or+Mars%29%3F&rft.date=2001&rft.au=Michael+Allison+%28%40+Goddard+Institute+for+Space+Studies%29&rft_id=http%3A%2F%2Fpweb.jps.net%2F~gangale3%2Fother%2Fallison2_frm.htm&rfr_id=info%3Asid%2Fen.wikipedia.org%3AJulian+year+%28astronomy%29" class="Z3988"></span></li></ul>    </section></div> <noscript><img src="https://login.m.wikimedia.org/wiki/Special:CentralAutoLogin/start?type=1x1&mobile=1" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Julian_year_(astronomy)&oldid=1258766658">https://en.wikipedia.org/w/index.php?title=Julian_year_(astronomy)&oldid=1258766658</a>"</div></div> </div> <div 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href="https://ast.wikipedia.org/wiki/A%C3%B1u_xulianu_(astronom%C3%ADa)" title="Añu xulianu (astronomía) – Asturian" lang="ast" hreflang="ast" data-title="Añu xulianu (astronomía)" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Any_juli%C3%A0" title="Any julià – Catalan" lang="ca" hreflang="ca" data-title="Any julià" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Juli%C3%A1nsk%C3%BD_rok" title="Juliánský rok – Czech" lang="cs" hreflang="cs" data-title="Juliánský rok" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-de badge-Q70894304 mw-list-item" title=""><a href="https://de.wikipedia.org/wiki/Julianisches_Jahr" title="Julianisches Jahr – German" lang="de" hreflang="de" data-title="Julianisches Jahr" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Juliuse_aasta" title="Juliuse aasta – Estonian" lang="et" hreflang="et" data-title="Juliuse aasta" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/A%C3%B1o_juliano_(astronom%C3%ADa)" title="Año juliano (astronomía) – Spanish" lang="es" hreflang="es" data-title="Año juliano (astronomía)" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Juliotar_urte_(astronomia)" title="Juliotar urte (astronomia) – Basque" lang="eu" hreflang="eu" data-title="Juliotar urte (astronomia)" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D8%B3%D8%A7%D9%84_%DA%98%D9%88%D9%84%DB%8C%D9%86%DB%8C_(%D8%A7%D8%AE%D8%AA%D8%B1%D8%B4%D9%86%D8%A7%D8%B3%DB%8C)" title="سال ژولینی (اخترشناسی) – Persian" lang="fa" hreflang="fa" data-title="سال ژولینی (اخترشناسی)" 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/Ann%C3%A9e_julienne" title="Année julienne – French" lang="fr" hreflang="fr" data-title="Année julienne" 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/%EC%9C%A8%EB%A6%AC%EC%9A%B0%EC%8A%A4%EB%85%84" title="율리우스년 – Korean" lang="ko" hreflang="ko" data-title="율리우스년" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Julijanska_godina_(astronomija)" title="Julijanska godina (astronomija) – Croatian" lang="hr" hreflang="hr" data-title="Julijanska godina (astronomija)" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Tahun_Julian" title="Tahun Julian – Indonesian" lang="id" hreflang="id" data-title="Tahun Julian" 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/Anno_giuliano" title="Anno giuliano – Italian" lang="it" hreflang="it" data-title="Anno giuliano" 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%A0%D7%94_%D7%99%D7%95%D7%9C%D7%99%D7%90%D7%A0%D7%99%D7%AA_(%D7%90%D7%A1%D7%98%D7%A8%D7%95%D7%A0%D7%95%D7%9E%D7%99%D7%94)" title="שנה יוליאנית (אסטרונומיה) – Hebrew" lang="he" hreflang="he" data-title="שנה יוליאנית (אסטרונומיה)" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/J%C5%ABlija_gads_(astronomija)" title="Jūlija gads (astronomija) – Latvian" lang="lv" hreflang="lv" data-title="Jūlija gads (astronomija)" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%88%D1%83%D0%BB%D0%B8%D1%98%D0%B0%D0%BD%D1%81%D0%BA%D0%B0_%D0%B3%D0%BE%D0%B4%D0%B8%D0%BD%D0%B0_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%98%D0%B0)" title="Јулијанска година (астрономија) – Macedonian" lang="mk" hreflang="mk" data-title="Јулијанска година (астрономија)" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%83%A6%E3%83%AA%E3%82%A6%E3%82%B9%E5%B9%B4" title="ユリウス年 – Japanese" lang="ja" hreflang="ja" data-title="ユリウス年" 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/Juliansk_%C3%A5r" title="Juliansk år – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Juliansk år" 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-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Juliansk_%C3%A5r" title="Juliansk år – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Juliansk år" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Rok_julia%C5%84ski" title="Rok juliański – Polish" lang="pl" hreflang="pl" data-title="Rok juliański" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Ano_juliano" title="Ano juliano – Portuguese" lang="pt" hreflang="pt" data-title="Ano juliano" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/An_iulian" title="An iulian – Romanian" lang="ro" hreflang="ro" data-title="An iulian" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%AE%D0%BB%D0%B8%D0%B0%D0%BD%D1%81%D0%BA%D0%B8%D0%B9_%D0%B3%D0%BE%D0%B4_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D0%B8%D1%8F)" title="Юлианский год (астрономия) – Russian" lang="ru" hreflang="ru" data-title="Юлианский год (астрономия)" 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/Julian_year" title="Julian year – Simple English" lang="en-simple" hreflang="en-simple" data-title="Julian year" 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-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Julijansko_leto" title="Julijansko leto – Slovenian" lang="sl" hreflang="sl" data-title="Julijansko leto" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%88%D1%83%D0%BB%D0%B8%D1%98%D0%B0%D0%BD%D1%81%D0%BA%D0%B0_%D0%B3%D0%BE%D0%B4%D0%B8%D0%BD%D0%B0" title="Јулијанска година – Serbian" lang="sr" hreflang="sr" data-title="Јулијанска година" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%AF%E0%AF%82%E0%AE%B2%E0%AE%BF%E0%AE%AF%E0%AE%A9%E0%AF%8D_%E0%AE%86%E0%AE%A3%E0%AF%8D%E0%AE%9F%E0%AF%81_(%E0%AE%B5%E0%AE%BE%E0%AE%A9%E0%AE%BF%E0%AE%AF%E0%AE%B2%E0%AF%8D)" title="யூலியன் ஆண்டு (வானியல்) – Tamil" lang="ta" hreflang="ta" data-title="யூலியன் ஆண்டு (வானியல்)" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-th mw-list-item"><a href="https://th.wikipedia.org/wiki/%E0%B8%9B%E0%B8%B5%E0%B8%88%E0%B8%B9%E0%B9%80%E0%B8%A5%E0%B8%B5%E0%B8%A2%E0%B8%99" title="ปีจูเลียน – Thai" lang="th" hreflang="th" data-title="ปีจูเลียน" data-language-autonym="ไทย" data-language-local-name="Thai" class="interlanguage-link-target"><span>ไทย</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/J%C3%BClyen_y%C4%B1l%C4%B1" title="Jülyen yılı – Turkish" lang="tr" hreflang="tr" data-title="Jülyen yılı" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%AE%D0%BB%D1%96%D0%B0%D0%BD%D1%81%D1%8C%D0%BA%D0%B8%D0%B9_%D1%80%D1%96%D0%BA_(%D0%B0%D1%81%D1%82%D1%80%D0%BE%D0%BD%D0%BE%D0%BC%D1%96%D1%8F)" title="Юліанський рік (астрономія) – Ukrainian" lang="uk" hreflang="uk" data-title="Юліанський рік (астрономія)" 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/N%C4%83m_Julius_(thi%C3%AAn_v%C4%83n)" title="Năm Julius (thiên văn) – Vietnamese" lang="vi" hreflang="vi" data-title="Năm Julius (thiên văn)" 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-classical mw-list-item"><a href="https://zh-classical.wikipedia.org/wiki/%E5%84%92%E7%95%A5%E5%B9%B4" title="儒略年 – Literary Chinese" lang="lzh" hreflang="lzh" data-title="儒略年" data-language-autonym="文言" data-language-local-name="Literary Chinese" class="interlanguage-link-target"><span>文言</span></a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/%E5%84%92%E7%95%A5%E5%B9%B4" title="儒略年 – Cantonese" lang="yue" hreflang="yue" data-title="儒略年" 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/%E5%84%92%E7%95%A5%E5%B9%B4" title="儒略年 – Chinese" lang="zh" hreflang="zh" data-title="儒略年" data-language-autonym="中文" data-language-local-name="Chinese" class="interlanguage-link-target"><span>中文</span></a></li></ul> </section> </div> <div class="minerva-footer-logo"><img src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" alt="Wikipedia" width="120" height="18" style="width: 7.5em; height: 1.125em;"/> 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