2024-05-12 02:47:15 -04:00
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2024-06-03 21:13:19 -04:00
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content="An interactive version of the Gregorian calendar, showing each day in various other calendars."/>
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content="An interactive version of the Julian calendar, showing each day in various other calendars."/>
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2024-05-12 02:47:15 -04:00
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2024-06-03 21:13:19 -04:00
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2024-05-12 02:47:15 -04:00
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<title>Gregorian Calendar</title>
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</head>
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<body>
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<div class="container">
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<a class="navbar-brand" href="#">Gregorian Calendar</a>
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<li class="nav-item">
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<a class="nav-link" href="#explanation">Explanation</a>
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</li>
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<li class="nav-item">
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<a class="nav-link" href="https://frcal.qt.ax">French Republican Calendar</a>
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</li>
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<noscript>You need to enable JavaScript to run this app.</noscript>
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<div id="root"></div>
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2024-06-16 22:43:35 -04:00
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<div class="main">
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<h2 id="explanation">Explanation</h2>
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<div class="card">
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<div class="card-body">
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<h4 class="card-title">What is this?</h4>
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<p class="lead">This is an implementation of the <a href="https://en.wikipedia.org/wiki/Gregorian_calendar">Gregorian
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calendar</a>—which is the default civil calendar in most countries—with conversions to various other
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calendars.</p>
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<p>Currently, it displays the following conversions for each day, if possible:</p>
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<ul>
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<li>the <a href="https://en.wikipedia.org/wiki/Julian_calendar">Julian calendar</a> date;</li>
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<li>the <a href="https://en.wikipedia.org/wiki/Julian_day">Julian day (JD) number</a>;</li>
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<li>the <a href="https://en.wikipedia.org/wiki/Mesoamerican_Long_Count_calendar">Mesoamerican Long Count
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calendar</a> date; and
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</li>
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<li>the <a href="https://en.wikipedia.org/wiki/French_Republican_calendar">French Republican
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calendar</a> date.
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</li>
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</ul>
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</div>
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</div>
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<div class="card">
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<div class="card-body">
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<h4 class="card-title">How are BCE years handled?</h4>
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<p class="lead">The astronomical convention is used, i.e. year 0 is 1 BCE, year -1 is 2 BCE, etc.</p>
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<p>Due to the way the common era (a.k.a. Anno Domini) year numbering system works, the year 1 BCE is
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followed directly by 1 CE with no year zero. This makes math hard. As such, the astronomical convention
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of making 1 BCE year 0 and extending this into the past was used.</p>
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</div>
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</div>
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<div class="card">
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<div class="card-body">
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<h4 class="card-title">What is the JD (Julian day number) value?</h4>
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<p>The integer <a href="https://en.wikipedia.org/wiki/Julian_day">Julian day (JD) number</a> is the
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continuous count of days since the beginning of the Julian period, which is very useful in astronomy and
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in software for calculating durations without worrying about weird calendar issues. In this respect,
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it's very similar to Unix time.</p>
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<p>JD 0 is assigned to the date Monday, January 1, 4713 BCE (Julian) or November 24, 4714 BCE (Gregorian).
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More specifically, if fractional JDs are considered, then the integer value specifically refers to the
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Universal Time noon on that date.</p>
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</div>
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</div>
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<div class="card">
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<div class="card-body">
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<h4 class="card-title">What is the LC (Mesoamerican Long Count) date?</h4>
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<p>The five (or more) numbers separated by dots is the corresponding
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<a href="https://en.wikipedia.org/wiki/Mesoamerican_Long_Count_calendar">Mesoamerican Long Count
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calendar</a> date. This is commonly known as the “Mayan calendar.” This calendar is not
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available for dates before August 11, 3114 BCE (Gregorian) or September 6, 3114 BCE (Julian).</p>
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</div>
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</div>
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<div class="card">
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<div class="card-body">
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<h4 class="card-title">What is the FR (French Republican calendar) date?</h4>
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<p>The <a href="https://en.wikipedia.org/wiki/French_Republican_calendar">French Republican
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calendar</a> was a calendar created and implemented during the French Revolution. It is also frequently
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referred to as the <em>French Revolutionary Calendar</em>, but this is a misnomer:
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year 1 of the calendar started on 22 September 1792, the day after the
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<a href="https://en.wikipedia.org/wiki/Proclamation_of_the_abolition_of_the_monarchy">abolition of the
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monarchy</a> and the founding of the <a href="https://en.wikipedia.org/wiki/French_First_Republic">French
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First Republic</a>.</p>
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<p>Specifically, the variant used here is <a href="https://frcal.qt.ax/">the one I computed from
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astronomy</a>.</p>
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</div>
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2024-05-12 02:47:15 -04:00
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<p class="text-muted">Copyright © 2022<%= new Date().getFullYear() > 2022 ? `–${new Date().getFullYear()}`
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: '' %>
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<a href="https://quantum5.ca">Quantum</a>.
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Licensed under <a href="https://www.gnu.org/licenses/agpl-3.0.en.html">GNU AGPLv3</a>.
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Source code available on <a href="https://github.com/quantum5/qcal">GitHub</a>.<br>
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