Lunar calendar

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 12 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; Vesak/Buddha's Birthday (Buddhist calendar); Diwali (Hindu calendars); and Rosh Hashanah (Hebrew calendar).

Calendario Lunar 2017
A Spanish lunar calendar for 2017


The earliest known lunar calendar was found at Warren Field in Scotland and has been dated to c. 8000 BC, during the Mesolithic period.[1] 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.[2][3]

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.[4]

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 of the fraction in the first columns, an integer number of months as listed in the denominator have been completed; the second column records the deviation accumulated with respect to the true synodic month duration and the time needed to achieve that deviation:

Fraction Approximate deviation
29/1 1 day after about 2 months
30/1 1 day after about 2 months
59/2 1 day after about 2.6 years
443/15 1 day after about 30 years
502/17 1 day after about 70 years
945/32 1 day after about 122 years
1447/49 1 day after about 3 millennia
25101/850 Not accurate due to the multi-millennial
change of the synodic month length.

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.[5] The tabular Islamic calendar's 360-month cycle is equivalent to 24×15 months, minus a correction of one day.

List of lunar calendars

See also


  1. ^ Nancy Owano, Scotland lunar-calendar find sparks Stone Age rethink,, 27 July 2013 Archived 9 August 2013 at the Wayback Machine
  2. ^ James Elkins, Our beautiful, dry, and distant texts (1998) 63ff.
  3. ^ "Oldest lunar calendar identified". BBC News. 2000-10-16. Retrieved 2013-03-14.
  4. ^ R.H.Codrington. The Melanesians: Their anthropology and folklore (1891) Oxford, Clarendon Press
  5. ^ Reform of the Julian Calendar as Envisioned by Isaac Newton by Ari Belenkiy and Eduardo Vila Echagüe (pdf); Notes and Records of the Royal Society of London (vol. 59, no. 3, pp. 223–254).

External links

Bon Festival

Obon (お盆) or just Bon (盆) is a Japanese Buddhist custom to honour the spirits of one's ancestors. This Buddhist-Confucian custom has evolved into a family reunion holiday during which people return to ancestral family places and visit and clean their ancestors' graves, and when the spirits of ancestors are supposed to revisit the household altars. It has been celebrated in Japan for more than 500 years and traditionally includes a dance, known as Bon-Odori.

The festival of Obon lasts for three days; however, its starting date varies within different regions of Japan. When the lunar calendar was changed to the Gregorian calendar at the beginning of the Meiji era, the localities in Japan reacted differently and this resulted in three different times of Obon. "Shichigatsu Bon" ("Bon in July") is based on the solar calendar and is celebrated around 15 July in eastern Japan (Kantō region such as Tokyo, Yokohama and the Tōhoku region), coinciding with Chūgen. "Hachigatsu Bon" (Bon in August) is based on the lunar calendar, is celebrated around the 15th of August and is the most commonly celebrated time. "Kyū Bon" (Old Bon) is celebrated on the 15th day of the seventh month of the lunar calendar, and so differs each year. "Kyū Bon" is celebrated in areas like the northern part of the Kantō region, Chūgoku region, Shikoku, and the Okinawa Prefecture. These three days are not listed as public holidays but it is customary that people are given leave.


A calendar is a system of organizing days for social, religious, commercial or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months and years. A date is the designation of a single, specific day within such a system. A calendar is also a physical record (often paper) of such a system. A calendar can also mean a list of planned events, such as a court calendar or a partly or fully chronological list of documents, such as a calendar of wills.

Periods in a calendar (such as years and months) are usually, though not necessarily, synchronised with the cycle of the sun or the moon. The most common type of pre-modern calendar was the lunisolar calendar, a lunar calendar that occasionally adds one intercalary month to remain synchronised with the solar year over the long term.

The term calendar is taken from calendae, the term for the first day of the month in the Roman calendar, related to the verb calare "to call out", referring to the "calling" of the new moon when it was first seen.

Latin calendarium meant "account book, register" (as accounts were settled and debts were collected on the calends of each month). The Latin term was adopted in Old French as calendier and from there in Middle English as calender by the 13th century (the spelling calendar is early modern). A calendar can be on paper or electronic device.

Chinese calendar

The traditional China calendar (officially known as the Rural Calendar [農曆; 农历; Nónglì; 'farming calendar']), or Former Calendar (舊曆; 旧历; Jiùlì), Traditional Calendar (老曆; 老历; Lǎolì) or Lunar Calendar (陰曆; 阴历; Yīnlì; 'yin calendar'), is a lunisolar calendar which reckons years, months and days according to astronomical phenomena. It is defined by GB/T 33661-2017, "Calculation and promulgation of the Chinese calendar", issued by the Standardisation Administration of China on 12 May 2017.

Although modern day China uses the Gregorian calendar, the traditional Chinese calendar governs holidays (such as the Chinese New Year) in China and in overseas Chinese communities. It lists the dates of traditional Chinese holidays and guides people in selecting auspicious days for weddings, funerals, moving, or starting a business.

Like Chinese characters, variants of this calendar are used in different parts of the Chinese cultural sphere. Korea, Vietnam, and the Ryukyu Islands adopted the calendar, and it evolved into Korean, Vietnamese, and Ryukyuan calendars. The main difference from the traditional Chinese calendar is the use of different meridians, which leads to some astronomical events—and calendar events based on them—falling on different dates. The traditional Japanese calendar also derived from the Chinese calendar (based on a Japanese meridian), but its official use in Japan was abolished in 1873 as part of reforms after the Meiji Restoration. Calendars in Mongolia and Tibet have absorbed elements of the traditional Chinese calendar, but are not direct descendants of it.Days begin and end at midnight, and months begin on the day of the new moon. Years begin on the second (or third) new moon after the winter solstice. Solar terms govern the beginning and end of each month. Written versions in ancient China included stems and branches of the year and the names of each month, including leap months as needed. Characters indicated whether a month was long (大, 30 days) or short (小, 29 days); stem branches for the first, eleventh, and 21st days, and the date, stem branch and time of the solar terms.

Egyptian calendar

The ancient Egyptian calendar was a solar calendar with a 365-day year. The year consisted of three seasons of 120 days each, plus an intercalary month of 5 epagomenal days treated as outside of the year proper. Each season was divided into four months of 30 days. These twelve months were initially numbered within each season but came to also be known by the names of their principal festivals. Each month was divided into three 10-day periods known as decans or decades. It has been suggested that during the Nineteenth Dynasty and the Twentieth Dynasty the last two days of each decan were usually treated as a kind of weekend for the royal craftsmen, with royal artisans free from work.

Because this calendrical year was nearly a quarter of a day shorter than the solar year, the Egyptian calendar lost about one day every four years relative to the Gregorian calendar. It is therefore sometimes referred to as the wandering year (Latin: annus vagus), as its months rotated about one day through the solar year every 4 years. Ptolemy III's Canopus Decree attempted to correct this through the introduction of a sixth epagomenal day every four years but the proposal was resisted by the Egyptian priests and people and abandoned until the establishment of the Alexandrian or Coptic calendar by Augustus. The introduction of a leap day to the Egyptian calendar made it equivalent to the reformed Julian calendar, although by extension it continues to diverge from the Gregorian calendar at the turn of most centuries.

This civil calendar ran concurrently with an Egyptian lunar calendar which was used for some religious rituals and festivals. Some Egyptologists have described it as lunisolar, with an intercalary month supposedly added every two or three years to maintain its consistency with the solar year, but no evidence of such intercalation before the 4th century BC has yet been discovered.

Galdan Namchot

Galdan Namchot is a festival celebrated in Tibet, Mongolia and many regions of Himalaya and particularly in Ladakh, India. It is to commemorate the birth as well as parinirvana (death) and the Buddhahood of Je Tsongkhapa (1357–1419 AD), a famous Scholar/teacher of Tibetan Buddhism whose activities led to the formation of the Gelug school of Tibetan Buddhism. Galdan Namchot also marks the beginning of the new year celebrations in Ladakh.

Hijri year

The Hijri year (Arabic: سَنة هِجْريّة‎) or era (التقويم الهجري at-taqwīm al-hijrī) is the era used in the Islamic lunar calendar, which begins its count from the Islamic New Year in 622 CE. During that year, Muhammad and his followers migrated from Mecca to Yathrib (now Medina). This event, known as the Hijra, is commemorated in Islam for its role in the founding of the first Muslim community (ummah).

In the West, this era is most commonly denoted as AH (Latin: Anno Hegirae , "in the year of the Hijra") in parallel with the Christian (AD), Common (CE) and Jewish eras (AM) and can similarly be placed before or after the date. In Muslim countries, it is also commonly abbreviated H ("Hijra") from its Arabic abbreviation hāʾ (هـ). Years prior to AH 1 are reckoned in English as BH ("Before the Hijra"), which should follow the date.Because the Islamic lunar calendar has only 354 or 355 days in its year, it slowly rotates relative to the Gregorian year. The year 2019 CE corresponds to the Islamic years AH 1440 – 1441. AH 1440 corresponds to 2018 – 2019 in the Common Era.

Hindu calendar

Hindu calendar is a collective term for the various lunisolar calendars traditionally used in the Indian subcontinent. They adopt a similar underlying concept for timekeeping, but differ in their relative emphasis to moon cycle or the sun cycle and the names of months and when they consider the New Year to start. Of the various regional calendars, the most studied and known Hindu calendars are the Shalivahana Shaka found in South India, Vikram Samvat (Bikrami) found in North and Central regions of India, Tamil calendar used in Tamil Nadu, and the Bengali calendar used in the Bengal – all of which emphasize the lunar cycle. Their new year starts in spring, with their heritage dating back to 1st millennium BCE. In contrast, in regions such as Kerala, the solar cycle is emphasized and this is called the Malayalam calendar, their new year starts in autumn, and these have origins in the second half of the 1st millennium CE. A Hindu calendar is sometimes referred to as Panchanga (पञ्चाङ्ग).The ancient Hindu calendar conceptual design is also found in the Jewish calendar, but different from the Gregorian calendar. Unlike Gregorian calendar which adds additional days to lunar month to adjust for the mismatch between twelve lunar cycles (354 lunar days) and nearly 365 solar days, the Hindu calendar maintains the integrity of the lunar month, but insert an extra full month by complex rules, every few years, to ensure that the festivals and crop-related rituals fall in the appropriate season.The Hindu calendars have been in use in the Indian subcontinent since ancient times, and remains in use by the Hindus in India and Nepal particularly to set the Hindu festival dates such as Holi, Maha Shivaratri, Vaisakhi, Raksha Bandhan, Pongal, Onam, Krishna Janmashtami, Durga Puja, Ram Navami, Pana Sankranti, Vishu and Diwali. Early Buddhist communities of India adopted the ancient Indian calendar, later Vikrami calendar and then local Buddhist calendars. Buddhist festivals continue to be scheduled according to a lunar system. The Buddhist calendar and the traditional lunisolar calendars of Cambodia, Laos, Myanmar, Sri Lanka and Thailand are also based on an older version of the Hindu calendar. Similarly, the ancient Jain traditions have followed the same lunisolar system as the Hindu calendar for festivals, texts and inscriptions. However, the Buddhist and Jain timekeeping systems have attempted to use the Buddha and the Mahavira's lifetimes as their reference points.The Hindu calendar is also important to the practice of Hindu astrology and zodiac system.

Indian New Year's days

There are numerous days throughout the year celebrated as New Year's Day in the different regions of India. Observance is determined by whether the lunar calendar is being following or the solar calendar. Those regions which follow the Solar calendar, the new year falls on Sankranti of the first month of the calendar, i.e., Vaishakha. Generally, this day falls during 14th or 15th of the month of April. Those following Lunar calendar consider the month of Chaitra (corresponding to March-April) as the first month of the year, so the new year is celebrated on the first day of this month. Similarly, few regions in India consider the period between consecutive Sankarantis as one month and few others take the period between consecutive Purnimas as a month.

Islamic calendar

The Islamic, Muslim, or Hijri calendar (Arabic: التقويم الهجري‎ at-taqwīm al-hijrī) is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. It is used to determine the proper days of Islamic holidays and rituals, such as the annual period of fasting and the proper time for the pilgrimage to Mecca. The civil calendar of almost all countries where the religion is predominantly Muslim is the Gregorian calendar. Notable exceptions to this rule are Iran and Afghanistan, which use the Solar Hijri calendar. Rents, wages and similar regular commitments are generally paid by the civil calendar.The Islamic calendar employs the Hijri era whose epoch was established as the Islamic New Year of 622 AD/CE. During that year, Muhammad and his followers migrated from Mecca to Yathrib (now Medina) and established the first Muslim community (ummah), an event commemorated as the Hijra. In the West, dates in this era are usually denoted AH (Latin: Anno Hegirae, "in the year of the Hijra") in parallel with the Christian (AD), Common (CE) and Jewish eras (AM). In Muslim countries, it is also sometimes denoted as H from its Arabic form (سَنة هِجْريّة, abbreviated هـ). In English, years prior to the Hijra are reckoned as BH ("Before the Hijra").The current Islamic year is 1440 AH. In the Gregorian calendar, 1440 AH runs from approximately 11 September 2018 to 30 August 2019.

Loi Krathong

Loi Krathong (Thai: ลอยกระทง, pronounced [lɔ̄ːj krā.tʰōŋ]) is a Siamese festival celebrated annually throughout the Kingdom of Thailand and in nearby countries with significant southwestern Tai cultures (Laos, Shan, Mon, Tanintharyi, Kelantan, Kedah and Xishuangbanna). The name could be translated as "to float a basket," and comes from the tradition of making krathong or buoyant, decorated baskets, which are then floated on a river.

Loi Krathong takes place on the evening of the full moon of the 12th month in the traditional Thai lunar calendar, thus the exact date of the festival changes every year. In the Western calendar this usually falls in the month of November. In Chang Mai, the festival lasts three days, and in 2018, the dates will be 21–23 November.

In Thailand, the festival is known as "Loi Krathong" (ลอยกระทง). Outside Thailand, this festival is celebrated under different names, including Myanmar as the "Tazaungdaing festival", Sri Lanka as "Il Full Moon Poya" and Cambodia as "Bon Om Touk".

Public holidays in Cambodia

Cambodia has numerous public holidays, including memorial holidays and religious holidays of Buddhist origin. The Khmer traditional calendar, known as Chhankitek, is a lunisolar calendar although the word Chhankitek itself means lunar calendar. While the calendar is based on the movement of the moon, calendar dates are also synchronized with the solar year to keep the seasons from drifting. Therefore, some public holidays are subject to change every year based on the lunar calendar. The government has announced plans to reduce public holidays by at least 7 days beginning in 2020.

Public holidays in Djibouti

This is a list of public holidays in Djibouti. The country uses two official calendar systems: the Gregorian calendar primarily, and the Islamic lunar calendar for religious holidays.

Public holidays in Hong Kong

Public holidays and statutory holidays in Hong Kong are holidays designated by the Government of Hong Kong. They allow workers rest from work, usually in conjunction with special occasions.

Public holidays in Somalia

Public holidays in Somalia are based on two official calendar systems: the Gregorian calendar primarily, and the Islamic lunar calendar for religious holidays.

Qiang folk religion

Qiang folk religion is the indigenous religion of the majority of the Qiang people, an ethnic group of Sichuan (China) tightly related to the Han Chinese and the Tibetans. It is pantheistic, involving the worship of a variety of gods of nature and of human affairs, including Qiang progenitors. White stones are worshipped as it is believed they can be invested with the power of some gods through rituals. They believe in an overarching God, called Mubyasei ("God of Heaven"), which is connected to the Chinese concept of Tian and clearly identified by the Qiang with the Taoist-originated Jade Deity.Religious ceremonies and rituals are directed by priests called duāngōng in Chinese. They are shamans who acquire their position through years of training with a teacher. Duāngōng are the custodians of Qiang theology, history and mythology. They also administer the coming of age ceremony for 18 year-old boys, called the "sitting on top of the mountain", which involves the boy's entire family going to mountain tops to sacrifice a sheep or cow, and to plant three cypress trees.Two of the most important religious holidays are the Qiang New Year, falling on the 24th day of the sixth month of the lunar calendar (though now it is fixed on October 1st), and the Mountain Sacrifice Festival, held between the second and the sixth month of the lunar calendar. The former festival is to give sacrifice to the God of Heaven, while the latter is dedicated to the god of mountains.

Thai calendar

In Thailand, two main calendar systems are used alongside each other: the Thai solar calendar, based on the Gregorian calendar, used for official and most day-to-day purposes, and the Thai lunar calendar (a version of the Buddhist calendar, technically a lunisolar calendar), used for traditional events and Buddhist religious practices.

The use of the solar calendar was introduced in 1889 by King Chulalongkorn (Rama V), replacing the lunar calendar in official contexts. Originally placing the beginning of year on 1 April, this was changed to 1 January in 1941, so the days and months now correspond exactly to the Gregorian calendar. Numbering of the years follow the Buddhist Era, introduced in 1913 to replace the Rattanakosin Era, which in turn replaced the Chula Sakarat in 1889. The reckoning of the Buddhist Era in Thailand is 543 years ahead of the Common Era (Anno Domini), so the year 2019 CE corresponds to B.E. 2562.

The lunar calendar contains twelve or thirteen months in a year, with 15 waxing moon and 14 or 15 waning moon days in a month, amounting to years of 354, 355 or 384 days. The years are usually noted by the animal of the Chinese zodiac, although there are several dates used to count the New Year.

As with the rest of the world, the seven-day week is used alongside both calendars. The solar calendar now governs most aspects of life in Thailand, and while official state documents invariably follow the Buddhist Era, the Common Era is also used by the private sector. The lunar calendar determines the dates of Buddhist holidays, traditional festivals and astrological practices, and the lunar date is still recorded on birth certificates and printed in most daily newspapers.

Thai lunar calendar

The Thai lunar calendar (Thai: ปฏิทินจันทรคติ, RTGS: patithin chanthrakhati, pronounced [pà.tì.tʰīn tɕān.tʰrá.kʰā.tìʔ], literally, Specific days according to lunar norms), or Tai calendar, is a lunisolar Buddhist calendar. It is used for calculating lunar-regulated holy days. Based on the SuriyaYatra, with likely influence from the traditional Hindu Surya Siddhanta, it has its own unique structure that does not require the Surya Siddhanta to calculate. Lunisolar calendars combine lunar and solar calendars for a nominal year of 12 months. An extra day or an extra 30-day month is intercalated at irregular intervals.

Traditional Chinese holidays

The traditional Chinese holidays are an essential part of harvests or prayer offerings. The most important Chinese holiday is the Chinese New Year (Spring Festival), which is also celebrated in Taiwan and overseas ethnic Chinese communities. All traditional holidays are scheduled according to the Chinese calendar (except the Qing Ming and Winter Solstice days, falling on the respective Jie qi in the Agricultural calendar).

Vietnamese calendar

The Vietnamese calendar is a lunisolar calendar that is based on the Geogorian calendar. As Vietnam's official calendar has been the Gregorian calendar since 1954, the Vietnamese calendar is used mainly to observe lunisolar holidays and commemorations, such as Tết and Mid-Autumn Festival.

Nearly universal
In wide use
In more
limited use
By specialty
Displays and
Year naming
International standards
Obsolete standards
Time in physics
Archaeology and geology
Astronomical chronology
Other units of time
Related topics
Key topics
Astronomic time
Geologic time
Genetic methods
Linguistic methods
Related topics
The Moon
Surface and
Time-telling and
Phases and

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.