Lunar calendar: Difference between revisions
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{{Short description|Calendar based only on the Moon}} | {{Short description|Calendar based only on the Moon}} | ||
{{redirects|Lunar date|uses not on Earth|timekeeping on the Moon}} | {{redirects|Lunar date|uses not on Earth|timekeeping on the Moon}} | ||
[[File: | [[File:Hijri calendar en.png|thumb|upright=1|[[Tabular Islamic calendar]] ]] | ||
A '''lunar calendar''' is a [[calendar]] | A '''lunar calendar''' is a [[calendar]] whose [[month]]s record the cycles of the [[Moon]]'s [[lunar phase|phase]]s ([[Lunar month#Synodic month|synodic month]]s, [[lunation]]s). This in contrast to [[solar calendar]]s, whose annual cycles are based on the [[solar year]] (which is about 11 to 12 days longer than twelve [[lunar month]]s). It is also to be contrasted with [[lunisolar calendar]]s, which also count [[lunar month]]s but recover the accumulated differences by adding ("[[intercalation (timekeeping)|intercalating]]") a thirteenth [[leap month]] every few years. The most widely observed lunar calendar is the [[Islamic calendar]].{{efn|Iran operates [[Solar Hijri calendar]], which is purely solar.}} | ||
Since each lunation is approximately {{frac|29|1|2}} days,<ref name=ESAA>{{cite book | title=Explanatory Supplement to the Astronomical Almanac |year=1992 | editor=P. Kenneth Seidelmann |page=577 |url=https://archive.org/details/131123ExplanatorySupplementAstronomicalAlmanac/page/n302/mode/1up | quote=For convenience, it is common to speak of a lunar year of twelve synodic months, or 354.36707 days.}} (which gives a mean synodic month as 29.53059 days or 29 days 12 hours 44 minutes and 3 seconds)</ref> it is common for the months of a lunar calendar to alternate between 29 and 30 days. Since the period of 12 such lunations, a '''lunar year''', is 354 days, 8 hours, 48 | Since each lunation is approximately {{frac|29|1|2}} days,<ref name=ESAA>{{cite book | title=Explanatory Supplement to the Astronomical Almanac |year=1992 | editor=P. Kenneth Seidelmann |page=577 |url=https://archive.org/details/131123ExplanatorySupplementAstronomicalAlmanac/page/n302/mode/1up | quote=For convenience, it is common to speak of a lunar year of twelve synodic months, or 354.36707 days.}} (which gives a mean synodic month as 29.53059 days or 29 days 12 hours 44 minutes and 3 seconds)</ref> it is common for the months of a lunar calendar to alternate between 29 and 30 days. Since the period of 12 such lunations, a '''lunar year''', is 354 days, 8 hours, 48 minutes, 34 seconds (354.36707 days),<ref name=ESAA /> lunar calendars are 11 to 12 days shorter than the [[tropical year|solar year]]. In lunar calendars, which do not make use of lunisolar calendars' intercalation, the lunar months cycle through all the seasons of a solar year over the course of a 33–34 lunar-year cycle (see, e.g., [[list of Islamic years]]). The details of when months begin vary from calendar to calendar, with some using [[new moon|new]], [[full moon|full]], or [[crescent]] moons and others employing detailed calculations. The term ''[[lunar new year]]'' is the first day of lunar calendar but is also [[Lunar New Year#Definition|widely used]], especially in the US, of lunisolar new years.<ref>{{cite encyclopedia |last=Kizer |first=Jessica M. |year=2014 |chapter=Lunar New Year |title=Asian American Society: An Encyclopedia|publisher=Sage Publications, Inc. |isbn=9781452281902 |oclc=880374731}}</ref> | ||
==History== | ==History== | ||
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== Start of the lunar month == | == Start of the lunar month == | ||
{{Unreferenced section|date=January 2026}} | |||
Lunar and lunisolar calendars differ as to which day is the first day of the month. Some are based on the first sighting of the [[lunar phase|lunar crescent]], such as the [[Islamic calendar|Hijri calendar]] observed by most of Islam. Alternatively, in some lunisolar calendars, such as the [[Hebrew calendar]] and [[Chinese calendar]], the first day of a month is the day when an astronomical [[new moon]] occurs in a particular time zone. In others, such as some [[Hindu calendar]]s, each month begins on the day after the full moon. | Lunar and lunisolar calendars differ as to which day is the first day of the month. Some are based on the first sighting of the [[lunar phase|lunar crescent]], such as the [[Islamic calendar|Hijri calendar]] observed by most of Islam. Alternatively, in some lunisolar calendars, such as the [[Hebrew calendar]] and [[Chinese calendar]], the first day of a month is the day when an astronomical [[new moon]] occurs in a particular time zone. In others, such as some [[Hindu calendar]]s, each month begins on the day after the full moon. | ||
== Length of the lunar month == | == Length of the lunar month == | ||
The length of each lunar cycle varies slightly from the average value. In addition, observations are subject to uncertainty and weather conditions. Thus, to minimise uncertainty, there have been attempts to create fixed arithmetical rules to determine the start of each calendar month. The best known of these is the [[Tabular Islamic calendar]]: in brief, it has a 30-year cycle with 11 [[leap year]]s of 355 days and 19 years of 354 days. In the long term, it is accurate to one day in about 2,500 solar years or 2,570 lunar years. It also deviates from observation by up to about one or two days in the short term. The algorithm was introduced by Muslim astronomers in the 8th century to predict the approximate date of the first crescent moon, which is used to determine the first day of each month in the [[Islamic calendar|Islamic lunar calendar]].<ref>{{cite web |title=The Arithmetical or Tabular Islamic Calendar |publisher=Mathematical Institute, [[Utrecht University]] |first=R. H. |last=van Gent |date=October 2023 |access-date=4 January 2024 |url=https://webspace.science.uu.nl/~gent0113/islam/islam_tabcal.htm}}</ref> | The length of each lunar cycle varies slightly from the average value. In addition, observations are subject to uncertainty and weather conditions{{snd}} in [[Sunni Islam]], the month begins with ''[[Hilal (Islam)|Hilal]]'', the actual observation of the first crescent.<ref>{{cite web |URL=https://www.muslimpro.com/crescent-moon-sighting-and-its-significance-for-ramadan/ |title=Crescent Moon Sighting and Its Significance for Ramadan |author=Ustazah Eka Budhi Setiani |website=Muslim Pro}}</ref> Thus, to minimise uncertainty, there have been attempts to create fixed arithmetical rules to determine the start of each calendar month. The best known of these is the [[Tabular Islamic calendar]]: in brief, it has a 30-year cycle with 11 [[leap year]]s of 355 days and 19 years of 354 days. In the long term, it is accurate to one day in about 2,500 solar years or 2,570 lunar years. It also deviates from observation by up to about one or two days in the short term. The algorithm was introduced by Muslim astronomers in the 8th century to predict the approximate date of the first crescent moon, which is used to determine the first day of each month in the [[Islamic calendar|Islamic lunar calendar]].<ref>{{cite web |title=The Arithmetical or Tabular Islamic Calendar |publisher=Mathematical Institute, [[Utrecht University]] |first=R. H. |last=van Gent |date=October 2023 |access-date=4 January 2024 |url=https://webspace.science.uu.nl/~gent0113/islam/islam_tabcal.htm}}</ref> | ||
== List of lunar calendars <span class="anchor" id="List of lunar calendars"></span> <!-- [[List of lunar calendars]] redirects here -->== | == List of lunar calendars <span class="anchor" id="List of lunar calendars"></span> <!-- [[List of lunar calendars]] redirects here -->== | ||
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* [[Javanese calendar]]{{efn|After 1633 CE reform}} | * [[Javanese calendar]]{{efn|After 1633 CE reform}} | ||
== Lunisolar calendars == | == Lunisolar calendars == <!--NB this article is about Lunar calendars so this section only gives a very brief overview of lunisolar calendars because the topic has its own article. --> | ||
{{main|Lunisolar calendar}} | {{main|Lunisolar calendar}} | ||
Most calendars referred to as "lunar" calendars are [[lunisolar calendar]]s. Their months are based on observations of the lunar cycle, with periodic [[Intercalation (timekeeping)|intercalation]] being used to restore them into general agreement with the solar year. The solar "[[Egyptian calendar|civic calendar]]" that was used in [[ancient Egypt]] showed traces of its origin in the earlier lunar calendar, which continued to be used alongside it for religious and agricultural purposes. Present-day lunisolar calendars include the [[Chinese calendar|Chinese]], [[Korean calendar|Korean]], [[Vietnamese calendar|Vietnamese]], [[Hindu calendar|Hindu]], [[Hebrew calendar|Hebrew]] and [[Thai lunar calendar|Thai]] calendars. | Most calendars referred to as "lunar" calendars are actually [[lunisolar calendar]]s. Their months are based on observations of the lunar cycle, with periodic [[Intercalation (timekeeping)|intercalation]] being used to restore them into general agreement with the solar year. The solar "[[Egyptian calendar|civic calendar]]" that was used in [[ancient Egypt]] showed traces of its origin in the earlier lunar calendar, which continued to be used alongside it for religious and agricultural purposes. Present-day lunisolar calendars include the [[Chinese calendar|Chinese]], [[Korean calendar|Korean]], [[Vietnamese calendar|Vietnamese]], [[Hindu calendar|Hindu]], [[Hebrew calendar|Hebrew]] and [[Thai lunar calendar|Thai]] calendars.{{Citation needed|date=January 2026}} | ||
The most common form of intercalation is to add an additional month every second or third year. Some lunisolar calendars are also calibrated by annual natural events which are affected by lunar cycles as well as the solar cycle. An example of this is the lunisolar calendar of the [[Banks Islands]], which includes three months in which the edible [[palolo worm]]s mass on the beaches. These events occur at the last quarter of the lunar month, as the reproductive cycle of the palolos is synchronized with the moon.<ref>R.H.Codrington | The most common form of intercalation is to add an additional month every second or third year. Some lunisolar calendars are also calibrated by annual natural events which are affected by lunar cycles as well as the solar cycle. An example of this is the lunisolar calendar of the [[Banks Islands]], which includes three months in which the edible [[palolo worm]]s mass on the beaches. These events occur at the last quarter of the lunar month, as the reproductive cycle of the palolos is synchronized with the moon.<ref>{{cite book |first=R.H. |last=Codrington |title=The Melanesians: Their anthropology and folklore |date=1891 |location=Oxford |publisher=Clarendon Press |oclc=853532 |url=https://archive.org/details/melanesiansstudi00codruoft/page/348/mode/2up?q=palolo |page=349}}</ref> | ||
== See also == | == See also == | ||
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== References == | == References == | ||
{{Reflist|30em}} | {{Reflist|30em}}{{calendars}} | ||
{{calendars}} | |||
{{Time measurement and standards}} | {{Time measurement and standards}} | ||
{{Chronology}} | {{Chronology}} | ||
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{{DEFAULTSORT:Lunar Calendar}} | {{DEFAULTSORT:Lunar Calendar}} | ||
[[Category:Lunar calendars| ]] | [[Category:Lunar calendars| ]] | ||
[[Category:Time measurement systems]] | |||
Latest revision as of 16:53, 21 February 2026
Template:Short description Template:Redirects
A lunar calendar is a calendar whose months record the cycles of the Moon's phases (synodic months, lunations). This in contrast to solar calendars, whose annual cycles are based on the solar year (which is about 11 to 12 days longer than twelve lunar months). It is also to be contrasted with lunisolar calendars, which also count lunar months but recover the accumulated differences by adding ("intercalating") a thirteenth leap month every few years. The most widely observed lunar calendar is the Islamic calendar.Template:Efn
Since each lunation is approximately <templatestyles src="Fraction/styles.css" />29+1⁄2 days,[1] it is common for the months of a lunar calendar to alternate between 29 and 30 days. Since the period of 12 such lunations, a lunar year, is 354 days, 8 hours, 48 minutes, 34 seconds (354.36707 days),[1] lunar calendars are 11 to 12 days shorter than the solar year. In lunar calendars, which do not make use of lunisolar calendars' intercalation, the lunar months cycle through all the seasons of a solar year over the course of a 33–34 lunar-year cycle (see, e.g., list of Islamic years). The details of when months begin vary from calendar to calendar, with some using new, full, or crescent moons and others employing detailed calculations. The term lunar new year is the first day of lunar calendar but is also widely used, especially in the US, of lunisolar new years.[2]
History
Scholars have argued that ancient hunters conducted regular astronomical observations of the Moon back in the Upper Palaeolithic.[3] Samuel L. Macey dates the earliest uses of the Moon as a time-measuring device back to 28,000–30,000 years ago.[4]
Start of the lunar month
Script error: No such module "Unsubst". Lunar and lunisolar calendars differ as to which day is the first day of the month. Some are based on the first sighting of the lunar crescent, such as the Hijri calendar observed by most of Islam. Alternatively, in some lunisolar calendars, such as the Hebrew calendar and Chinese calendar, the first day of a month is the day when an astronomical new moon occurs in a particular time zone. In others, such as some Hindu calendars, each month begins on the day after the full moon.
Length of the lunar month
The length of each lunar cycle varies slightly from the average value. In addition, observations are subject to uncertainty and weather conditionsTemplate:Snd in Sunni Islam, the month begins with Hilal, the actual observation of the first crescent.[5] Thus, to minimise uncertainty, there have been attempts to create fixed arithmetical rules to determine the start of each calendar month. The best known of these is the Tabular Islamic calendar: in brief, it has a 30-year cycle with 11 leap years of 355 days and 19 years of 354 days. In the long term, it is accurate to one day in about 2,500 solar years or 2,570 lunar years. It also deviates from observation by up to about one or two days in the short term. The algorithm was introduced by Muslim astronomers in the 8th century to predict the approximate date of the first crescent moon, which is used to determine the first day of each month in the Islamic lunar calendar.[6]
List of lunar calendars
Lunisolar calendars
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Most calendars referred to as "lunar" calendars are actually lunisolar calendars. Their months are based on observations of the lunar cycle, with periodic intercalation being used to restore them into general agreement with the solar year. The solar "civic calendar" that was used in ancient Egypt showed traces of its origin in the earlier lunar calendar, which continued to be used alongside it for religious and agricultural purposes. Present-day lunisolar calendars include the Chinese, Korean, Vietnamese, Hindu, Hebrew and Thai calendars.Script error: No such module "Unsubst".
The most common form of intercalation is to add an additional month every second or third year. Some lunisolar calendars are also calibrated by annual natural events which are affected by lunar cycles as well as the solar cycle. An example of this is the lunisolar calendar of the Banks Islands, which includes three months in which the edible palolo worms mass on the beaches. These events occur at the last quarter of the lunar month, as the reproductive cycle of the palolos is synchronized with the moon.[7]
See also
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Notes
References
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- ↑ a b Script error: No such module "citation/CS1". (which gives a mean synodic month as 29.53059 days or 29 days 12 hours 44 minutes and 3 seconds)
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