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{{short description|Calendar based on the phases of the Moon}}
{{short description|Calendar based on the phases of the Moon}}{{redirects|lunar date|uses not on Earth|timekeeping on the Moon}}


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A '''lunar calendar''' is a [[calendar]] based on the [[month]]ly cycles of the [[Moon]]'s [[lunar phase|phase]]s ([[Lunar month#Synodic month|synodic month]]s, [[lunation]]s), in contrast to [[solar calendar]]s, whose annual cycles are based on the [[solar year]]. There are multiple versions of the lunar calendar across cultures. A purely lunar calendar is distinguished from a [[lunisolar calendar]], whose [[lunar month]]s are brought into alignment with the solar year through some process of [[intercalation (timekeeping)|intercalation]]{{snd}}such as by insertion of a [[leap month]]. 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.
[[File:Iran Kalender 1863 Linden-Museum.jpg|thumb|right|400px|Iranian [[Islamic calendar]] dedicated to [[Qajar Iran|Qajar]] ruler [[Naser al-Din Shah]] in 1280, [[Linden Museum]], [[Stuttgart]], Germany]]{{redirects|lunar date|uses not on Earth|timekeeping on the Moon}}


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Since each lunation is approximately {{frac|29|1|2}}&nbsp;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&nbsp;days. Since the period of 12 such lunations, a '''lunar year''', is 354&nbsp;days, 8&nbsp;hours, 48&nbsp;minutes, 34&nbsp;seconds (354.36707&nbsp;days),<ref name=ESAA /> purely lunar calendars are 11 to 12 days shorter than the [[tropical year|solar year]]. In purely lunar calendars, which do not make use of intercalation, the lunar months cycle through all the seasons of a solar year over the course of a 33–34 lunar-year cycle.
⚫
A '''lunar calendar''' is a [[calendar]] based on the [[month]]ly cycles of the [[Moon]]'s [[lunar phase|phase]]s ([[Lunar month#Synodic month|synodic month]]s, [[lunation]]s), in contrast to [[solar calendar]]s, whose annual cycles are based on the [[solar year]]. The most widely observed purely lunar calendar is the [[Islamic calendar]].{{efn|Iran operates [[Solar Hijri calendar]], which is purely solar.}} A purely lunar calendar is distinguished from a [[lunisolar calendar]], whose [[lunar month]]s are brought into alignment with the solar year through some process of [[intercalation (timekeeping)|intercalation]]{{snd}}such as by insertion of a [[leap month]]. 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.

⚫
Since each lunation is approximately {{frac|29|1|2}}&nbsp;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&nbsp;days. Since the period of 12 such lunations, a '''lunar year''', is 354&nbsp;days, 8&nbsp;hours, 48&nbsp;minutes, 34&nbsp;seconds (354.36707&nbsp;days),<ref name=ESAA /> purely lunar calendars are 11 to 12 days shorter than the [[tropical year|solar year]]. In purely lunar calendars, which do not make use of 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]]).


==History==
==History==
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== Start of the lunar month ==
== Start of the lunar month ==
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 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]]. 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 CE 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. Thus, to minimize uncertainty, there have been attempts to create fixed arithmetical rules to determine the start of each calendar month.


== 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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<!-- [[Gezer calendar|Gezer Calendar]] page does not support being lunar -->
<!-- [[Gezer calendar|Gezer Calendar]] page does not support being lunar -->
<!-- [[Igbo calendar]] luninsolar -->
<!-- [[Igbo calendar]] luninsolar -->
* [[Islamic calendar|Islamic Hijri calendar]]
* [[Javanese calendar]]
* [[Javanese calendar]]
<!-- Jewish calendar is lunisolar -->
<!-- Jewish calendar is lunisolar -->

Revision as of 06:21, 19 April 2024

"lunar date" redirects here. For uses not on Earth, see timekeeping on the Moon.

A lunar calendar is a calendar based on the monthly cycles of the Moon's phases (synodic months, lunations), in contrast to solar calendars, whose annual cycles are based on the solar year. There are multiple versions of the lunar calendar across cultures. A purely lunar calendar is distinguished from a lunisolar calendar, whose lunar months are brought into alignment with the solar year through some process of intercalation – such as by insertion of a leap month. The details of when months begin vary from calendar to calendar, with some using new, full, or crescent moons and others employing detailed calculations.

Since each lunation is approximately 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] purely lunar calendars are 11 to 12 days shorter than the solar year. In purely lunar calendars, which do not make use of intercalation, the lunar months cycle through all the seasons of a solar year over the course of a 33–34 lunar-year cycle.

History

A lunisolar calendar was found at Warren Field in Scotland and has been dated to c. 8000 BC, during the Mesolithic period.[2][3] Some scholars argue for lunar calendars still earlier—Rappenglück in the marks on a c. 17,000 year-old cave painting at Lascaux and Marshack in the marks on a c. 27,000 year-old bone baton—but their findings remain controversial.[4][5] Scholars have argued that ancient hunters conducted regular astronomical observations of the Moon back in the Upper Palaeolithic.[6] Samuel L. Macey dates the earliest uses of the Moon as a time-measuring device back to 28,000–30,000 years ago.[7]

Start of the lunar month

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. 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 conditions. Thus, to minimize uncertainty, there have been attempts to create fixed arithmetical rules to determine the start of each calendar month.

List of lunar calendars

Lunisolar calendars

Main article: Lunisolar calendar

Most calendars referred to as "lunar" calendars are in fact 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.

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.[8]

See also

Notes

References

  1. ^ a b P. Kenneth Seidelmann, ed. (1992). Explanatory Supplement to the Astronomical Almanac. p. 577. 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)
  2. ^ Nancy Owano, Scotland lunar-calendar find sparks Stone Age rethink, Phys.org, 27 July 2013 Archived 9 August 2013 at the Wayback Machine
  3. ^ Gaffney, V.; et al. (2013). "Time and a Place: A luni-solar 'time-reckoner' from 8th millennium BC Scotland". Internet Archaeology (34). doi:10.11141/ia.34.1. Archived from the original on 18 July 2013. Retrieved 16 July 2013. In doing so the monument anticipates problems associated with simple lunar calendars by providing an annual astronomic correction in order to maintain the link between the passage of time indicated by the Moon, the asynchronous solar year, and the associated seasons.
  4. ^ James Elkins, Our beautiful, dry, and distant texts (1998) 63ff.
  5. ^ "Oldest lunar calendar identified". BBC News. 2000-10-16. Retrieved 2013-03-14.
  6. ^ Gurshtein, Alex (2005-01-01). "Did the Pre-Indo-Europeans Influence the Formation of the Western Zodiac?". Journal of Indo-European Studies. 33: 106.
  7. ^ Macey, Samuel L. (1994). Encyclopedia of Time. Taylor & Francis. p. 75. ISBN 9780815306153.
  8. ^ R.H.Codrington. The Melanesians: Their anthropology and folklore (1891) Oxford, Clarendon Press

External links

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