Lunar calendar | Wikipedia audio article

A lunar calendar is a calendar based upon
the monthly cycles of the Moon’s phases (synodic months), in contrast to solar calendars, whose
annual cycles are based only directly upon the solar year. The most commonly used calendar,
the Gregorian calendar, is a solar calendar system that originally evolved out of a lunar
calendar system. A purely lunar calendar is also distinguished from a lunisolar calendar,
whose lunar months are brought into alignment with the solar year through some process of
intercalation. The details of when months begin varies 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 (29 days, 12 hours, 44 minutes,
3 seconds, or 29.530588 days), it is common for the months of a lunar calendar to alternate
between 29 and 30 days. Since the period of twelve such lunations, a lunar year, is only
354 days, 8 hours, 48 minutes, 34 seconds (354.367056 days), purely lunar calendars
lose around 11 days per year relative to the Gregorian calendar. In purely lunar calendars
like the Islamic calendar, the lack of intercalation causes the lunar months to cycle through all
the seasons of the Gregorian year over the course of a 33 lunar-year cycle.
Although the Gregorian calendar is in common and legal use in most countries, traditional
lunar and lunisolar calendars continue to be used throughout the Old World to determine
religious festivals and national holidays. Examples of such holidays include Ramadan
(Islamic calendar); Easter, the Chinese, Japanese, Korean, Vietnamese, and Mongolian New Year
(Chinese, Japanese, Korean, Vietnamese, and Mongolian calendars); the Nepali New Year
(Nepali calendar); the Mid-Autumn Festival and Chuseok (Chinese and Korean calendars);
Loi Krathong (Thai calendar); Sunuwar calendar; Diwali (Hindu calendars); and Rosh Hashanah
(Hebrew calendar).==History==
The earliest known lunar calendar was found at Warren Field in Scotland and has been dated
to c. 8000 BC, during its Mesolithic period. Some scholars argue for lunar calendars still
further back—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.==Lunisolar calendars==Most calendars referred to as “lunar” calendars
are in fact lunisolar calendars. Their months are based on observations of the lunar cycle,
with intercalation being used to bring 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, Hindu, and
Thai calendars. Synodic months are 29 or 30 days in length,
making a lunar year of 12 months about 11 days shorter than a solar year. Some lunar
calendars do not use intercalation, such as most Islamic calendars. For those that do,
such as the Hebrew calendar, 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 lunar calendar of the Banks Islands, which includes three months in which the edible
palolo worm 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.==Start of the lunar month==
Lunar and lunisolar calendars differ as to which day is the first day of the month. In
some lunisolar calendars, such as the 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 or the new moon.
Others were based in the past on the first sighting of a lunar crescent, such as the
Hebrew calendar and the Hijri calendar.==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 avoid uncertainty about the calendar,
there have been attempts to create fixed arithmetical rules to determine the start of each calendar
month. The average length of the synodic month is
29.530587981 days. Thus it is convenient if months generally alternate between 29 and
30 days (sometimes termed respectively “hollow” and “full”). The distribution of hollow
and full months can be determined using continued fractions, and examining successive approximations
for the length of the month in terms of fractions of a day. In the list below, after the number
of days listed in the numerator, an integer number of months as listed in the denominator
have been completed: These fractions can be used to construct a
lunar calendar, or in combination with a solar calendar to produce a lunisolar calendar.
A 49 month cycle was proposed as the basis of an alternative Easter computation by Isaac
Newton around 1700. The tabular Islamic calendar’s 360 month cycle is equivalent to 24×15 months,
minus a correction of one day.==List of lunar calendars==
Gezer Calendar Haida
Islamic calendar Nepal Sambat
Javanese calendar Assyrian calendar
Yoruba calendar Igbo calendar==See also==Babylonian calendar
Celtic calendar Chinese, Japanese, Korean, Vietnamese, and
Mongolian calendars Egyptian calendar
Epact Hindu calendar
Iranian and Hebrew calendars Islamic calendar
Lunar phase Mayan calendar
Paschal Full Moon Roman calendar
Thai lunar calendar Tibetan calendar==References====External links==
Convert today’s date to lunar calendar date Calendar of Betting
Calendar of Game Football Betting’s Calendar

Stephen Childs

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