The Buddhist calendar is a set of

lunisolar calendar A lunisolar calendar is a calendar in many cultures, that combines monthly lunar cycles with the solar year. As with all calendars which divide the year into months, there is an additional requirement that the year have a whole number of mont ...

s primarily used in

Tibet Tibet (; ''Böd''; ), or Greater Tibet, is a region in the western part of East Asia, covering much of the Tibetan Plateau and spanning about . It is the homeland of the Tibetan people. Also resident on the plateau are other ethnic groups s ...

Cambodia Cambodia, officially the Kingdom of Cambodia, is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. It is bordered by Thailand to the northwest, Laos to the north, and Vietnam to the east, and has a coastline ...

Laos Laos, officially the Lao People's Democratic Republic (LPDR), is the only landlocked country in Southeast Asia. It is bordered by Myanmar and China to the northwest, Vietnam to the east, Cambodia to the southeast, and Thailand to the west and ...

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

Bangladesh Bangladesh, officially the People's Republic of Bangladesh, is a country in South Asia. It is the List of countries and dependencies by population, eighth-most populous country in the world and among the List of countries and dependencies by ...

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

Sri Lanka Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka, also known historically as Ceylon, is an island country in South Asia. It lies in the Indian Ocean, southwest of the Bay of Bengal, separated from the Indian subcontinent, ...

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

and

Vietnam Vietnam, officially the Socialist Republic of Vietnam (SRV), is a country at the eastern edge of mainland Southeast Asia, with an area of about and a population of over 100 million, making it the world's List of countries and depende ...

as well as in

Malaysia Malaysia is a country in Southeast Asia. Featuring the Tanjung Piai, southernmost point of continental Eurasia, it is a federation, federal constitutional monarchy consisting of States and federal territories of Malaysia, 13 states and thre ...

and

Singapore Singapore, officially the Republic of Singapore, is an island country and city-state in Southeast Asia. The country's territory comprises one main island, 63 satellite islands and islets, and one outlying islet. It is about one degree ...

and by Chinese populations for religious or official occasions. While the calendars share a common lineage, they also have minor but important variations such as intercalation schedules, month names and numbering, use of cycles, etc. In Thailand, the name Buddhist Era is a year numbering system shared by the traditional Thai lunar calendar and by the

Thai solar calendar The Thai solar calendar (, , "solar calendar") was adopted by King Chulalongkorn (Rama V) in 1888 Common Era, CE as the Siamese version of the Gregorian calendar, replacing the Thai lunar calendar as the legal Thai calendar (though the latter i ...

. The Southeast Asian

s are largely based on an older version of the

Hindu calendar The Hindu calendar, also called Panchangam, Panchanga (), is one of various lunisolar calendars that are traditionally used in the Indian subcontinent and Southeast Asia, with further regional variations for social and Hindu religious purposes ...

, which uses the

sidereal year A sidereal year (, ; ), also called a sidereal orbital period, is the time that Earth or another planetary body takes to orbit the Sun once with respect to the fixed stars. Hence, for Earth, it is also the time taken for the Sun to return to t ...

as the solar year. One major difference is that the Southeast Asian systems, unlike their Indian cousins, do not use apparent reckoning to stay in sync with the sidereal year. Instead, they employ their versions of the

Metonic cycle The Metonic cycle or enneadecaeteris (from , from ἐννεακαίδεκα, "nineteen") is a period of almost exactly 19 years after which the lunar phases recur at the same time of the year. The recurrence is not perfect, and by precise obser ...

. However, since the Metonic cycle is not very accurate for sidereal years, the Southeast Asian calendar is slowly drifting out of sync with the sidereal, approximately one day every 100 years. Yet no coordinated structural reforms of the lunisolar calendar have been undertaken. Today, the traditional Buddhist lunisolar calendar is used mainly for

Theravada Buddhist ''Theravāda'' (; 'School of the Elders'; ) is Buddhism's oldest existing school. The school's adherents, termed ''Theravādins'' (anglicized from Pali ''theravādī''), have preserved their version of the Buddha's teaching or ''Dhamma'' in th ...

festivals. The Thai Buddhist Era, a renumbered

Gregorian calendar The Gregorian calendar is the calendar used in most parts of the world. It went into effect in October 1582 following the papal bull issued by Pope Gregory XIII, which introduced it as a modification of, and replacement for, the Julian cale ...

, is the official calendar in Thailand.

Structure

The calculation methodology of the current versions of Southeast Asian Buddhist calendars is largely based on that of the

Burmese calendar The Burmese calendar (, , or , ; Burmese Era (BE) or Myanmar Era (ME)) is a lunisolar calendar in which the months are based on lunar months and years are based on sidereal years. The calendar is largely based on an older version of the Hind ...

, which was in use in various Southeast Asian kingdoms down to the 19th century under the names of

Chula Sakarat Chula Sakarat or Chulasakarat (; , ; , ; , , , abbrv. จ.ศ. ''Choso'') is a lunisolar calendar derived from the Burmese calendar, whose variants were in use by most mainland Southeast Asian kingdoms down to the late 19th century. The calendar is ...

and Jolak Sakaraj. The Burmese calendar in turn was based on the "original" ''

Surya Siddhanta The ''Surya Siddhanta'' (; ) is a Sanskrit treatise in Indian astronomy dated to 4th to 5th century,Menso Folkerts, Craig G. Fraser, Jeremy John Gray, John L. Berggren, Wilbur R. Knorr (2017)Mathematics Encyclopaedia Britannica, Quote: "(...) i ...

'' system of ancient India (believed to be Ardharatrika school).Ohashi 2007: 354–355 One key difference with Indian systems is that the Burmese system has followed a variation of the

. It is unclear from where, when or how the Metonic system was introduced; hypotheses range from China to Europe. The Burmese system, and indeed the Southeast Asian systems, thus use a "strange" combination of

s from the Indian calendar in combination with the Metonic cycle better for

tropical year A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky – as viewed from the Earth or another celestial body of the Solar System – thus completing a full cycle of astronom ...

s.Ohashi 2001: 398–399

Epoch

In all

Theravada ''Theravāda'' (; 'School of the Elders'; ) is Buddhism's oldest existing school. The school's adherents, termed ''Theravādins'' (anglicized from Pali ''theravādī''), have preserved their version of the Buddha's teaching or ''Dharma (Buddhi ...

traditions, the calendar's

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

(foundational moment) was the day in which the

Buddha Siddhartha Gautama, most commonly referred to as the Buddha (),* * * was a wandering ascetic and religious teacher who lived in South Asia during the 6th or 5th century BCE and founded Buddhism. According to Buddhist legends, he was ...

attained '' parinibbāna''. However, not all traditions agree on when it actually took place. In Burmese Buddhist tradition, it was 13 May 544 BCE (Tuesday, Full moon of Kason 148 Anjanasakaraj).Kala Vol. 1 2006: 38 In Thai Buddhist tradition, it was 11 March 544 BCE, the date which the current Thai lunisolar and solar calendars use as their epochal date. Yet, the Thai calendars for some reason have fixed the difference between their Buddhist Era (BE) numbering and the

Common Era Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the ...

(CE) numbering at full 543.Eade 1995: 15–16 In Myanmar, the difference between BE and CE can be 543 or 542 for CE dates, and 542 or 541 for BCE dates, depending on the month of the Buddhist Era (as the Buddhist calendar straddles the Gregorian calendar—currently from April to April).

Month

Types

The calendar recognizes two types of months:

synodic month In lunar calendars, a lunar month is the time between two successive Syzygy (astronomy), syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona people, S ...

and sidereal month. The Synodic months are used to compose the years while the 27 lunar sidereal days (Sanskrit: ''

nakshatra Nakshatra () is the term for Lunar mansion in Hindu astrology and Buddhist astrology. A nakshatra is one of 27 (sometimes also 28) sectors along the ecliptic. Their names are related to a prominent star or asterisms in or near the respective s ...

''), alongside the 12 signs of the zodiac, are used for astrological calculations.Irwin 1909: 8–9 (The Burmese calendar also recognizes a solar month called ''Thuriya Matha'', which is defined as 1/12th of a year.Irwin 1909: 5 But the solar month varies by the type of year such as tropical year, sidereal year, etc.)

Waxing and waning

The days of the month are counted in two halves, waxing and waning. The 15th of the waxing is the civil full moon day. The civil new moon day is the last day of the month (14th or 15th waning). Because of the inaccuracy of the calendrical calculation systems, the mean and real (true) New Moons rarely coincide. The mean New Moon often precedes the real New Moon.Clancy 1906: 56–57

Number of days per month

As the Synodic lunar month is approximately 29.5 days, the calendar uses alternating months of 29 and 30 days.

Month numbering

Various regional versions of Chula Sakarat/Burmese calendar existed across various regions of mainland Southeast Asia. Unlike Burmese systems, Kengtung, Sipsongpanna, Lan Na,

Lan Xang Lan Xang () or Lancang was a Lao people, Lao kingdom that held the area of present-day Laos from 1353 to 1707. For three and a half centuries, Lan Xang was one of the largest kingdoms in Southeast Asia. The kingdom is the basis for Laos's nat ...

and Sukhothai systems refer to the months by numbers, not by names. This means reading ancient texts and inscriptions in Thailand requires constant vigilance, not just in making sure one is correctly operating for the correct region, but also for variations within regions itself when incursions cause a variation in practice.Eade 1989: 9–10Eade 1995: 28–29

Year

The Buddhist calendar is a

in which the months are based on

lunar month In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month. Variations In Shona, Middle Eastern, and Euro ...

s and years are based on

solar year A tropical year or solar year (or tropical period) is the time that the Sun takes to return to the same position in the sky – as viewed from the Earth or another celestial body of the Solar System – thus completing a full cycle of astronom ...

s. One of its primary objectives is to synchronize the lunar part with the solar part. The lunar months, normally twelve of them, consist alternately of 29 days and 30 days, such that a normal lunar year will contain 354 days, as opposed to the solar year of ~365.25 days. Therefore, some form of addition to the lunar year (of intercalation) is necessary. The overall basis for it is provided by cycles of 57 years. Eleven extra days are inserted in every 57 years, and seven extra months of 30 days are inserted in every 19 years (21 months in 57 years). This provides 20819 complete days to both calendars.Eade 1995: 15 This 57-year cycle would provide a mean year of about 365.2456 days and a mean month of about 29.530496 days, if not corrected. As such, the calendar adds an

intercalary month Intercalation or embolism in timekeeping is the insertion of a leap day, week, or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of days or months. Solar ca ...

leap year A leap year (also known as an intercalary year or bissextile year) is a calendar year that contains an additional day (or, in the case of a lunisolar calendar, a month) compared to a common year. The 366th day (or 13th month) is added to keep t ...

s and sometimes also an intercalary day in great leap years. The intercalary month not only corrects the length of the year but also corrects the accumulating error of the month to extent of half a day. The average length of the month is further corrected by adding a day to Nayon at irregular intervals—a little more than seven times in two cycles (39 years). The intercalary day is never inserted except in a year which has an intercalary month. The Hindu calendar inserts an intercalary month at any time of year as soon as the accumulated fractions amount to one month. The Burmese calendar however always inserts the intercalary month at the same time of the year, after the

summer solstice The summer solstice or estival solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere ( Northern and Southern). The summer solstice is the day with the longest peri ...

while the Arakanese calendar inserts it after the vernal equinox.Irwin 1909: 2–3

Burmese

The Burmese calendar year consists of 354, 384 or 385 days. Note: The Arakanese calendar adds the intercalary day in Tagu, not in Nayon.

Cambodian, Lao and Thai

The Cambodian, Lao and Thai lunisolar calendars use a slightly different method to place the intercalary day. Instead of it in a leap year as in the Burmese system, the Thai system places it in a separate year. Thus, the Thai small leap year has 355 days while the Thai great leap year has 384 days.

New Year's Day

Since the main purpose of Buddhist calendar is to keep pace with the solar year, the new year is always marked by the

, which falls at the time when the Sun enters Aries. The date, which at the present falls on the 17th of April, has slowly drifted over the centuries. In the 20th century, the New Year's Day fell on April 15 or 16th but in the 17th century, it fell on April 9 or 10th.Eade 1989: 135–145, 165–175 Thailand and Cambodia no longer use the traditional lunisolar calendar to mark the New Year's Day.

Cycle

The Cambodian, Lao and Thai systems give animal names to the years from a cycle of 12.Eade 1995: 22 The practice also existed in Burma in the Pagan period but later died out.Luce 1970: 330 The Cambodian calendar also maintains a 10-year naming cycle (numbered one to ten). Cambodians use multiple systems to identify a given year. For instance, 2017 is identified as 2561 Buddhist Era, the year of Rooster, Nuppasak (Year 9). The Thai lunar calendar also uses a similar numbered 10-year cycle. Each number in the cycle corresponds to the last digit of the year in the ''

'' calendar.

Accuracy

The Southeast Asian Buddhist calendars use lunar months but try to keep pace with the solar year, by inserting intercalary months and days on the Metonic cycle (in the case of the Burmese calendar, on a modified Metonic cycle). However, the solar year as defined by the Buddhist calendars is really a

, which is nearly 24 minutes longer than the actual mean

. Therefore, like all sidereal-based calendars, the lunisolar calendars are slowly drifting away from the seasons.Irwin 1909: 26–27 The calendars are drifting one day approximately every 60 years and 4 months. The accumulating drift against the seasons means the New Year's Day which used to fall on 22 March (near the vernal equinox) in 638 CE now falls on 17 April in 2013 CE. There is no known internationally concerted effort to stop this drift. Thailand has moved its "Buddhist Era" to the Gregorian calendar under the name of

. In Myanmar, Burmese calendarists have tried to deal with the issue by periodically modifying the intercalation schedule in the Metonic cycle. One major downside of this approach is that it is not possible to publish future calendars more than a few years (often even a year) ahead.

History

The Buddhist Era was first introduced to Southeast Asia along with Buddhism in the early centuries CE. It was not a separate calendar but simply a year numbering system that employed the organization and calculation methods of the prevailing lunisolar calendars in use throughout the region. In the early centuries CE, the reference civil calendar of the Buddhist calendar prevalent in Southeast Asia was the Saka Era (Mahāsakaraj Era), which is said to have been adopted by the Pyu state of

Sri Ksetra Sri Ksetra (, , ; Sanskrit: श्री क्षेत्र, Htin Aung, Maung (1970). ''Burmese History before 1287: A Defence of the Chronicles.'' Oxford: The Asoka Society, 8 - 10. or 'Field of Glory'), located along the Irrawaddy River at p ...

in 80 CE. The Saka Era was gradually replaced by the Burmese Era or Culāsakaraj, first in Myanmar in 640 CE,Hmannan Vol. 1 2003: 216 and in other Theravada kingdoms of Southeast Asia between the 13th and 16th centuries.{efn, (Eade 1989: 11): The earliest use of the Burmese calendar in lands part of present-day Thailand dates to the mid-13th century. (Smith 1966: 11): Ayutthaya adopted the Burmese calendar in the 16th century. Theravada Buddhist tradition also recognizes pre-Buddhist Anjana Sakaraj (Añjana's Era) since the events of the Buddha's life are recorded in that era. {, class="wikitable" , - ! width="200", Name ! width="200", Epochal date ! width="600", Notes , - , Anjana Sakaraj , 10 March 691 BCE , Said to have been started by the Buddha's maternal grandfather King Añjana
Used to date the events during the Buddha's lifetime , - , Buddhist Era , 13 May 544 BCE
11 March 545 BCE , 544 BCE in Myanmar; 545 BCE in Thailand , - , Śaka Era , 17 March 78 CE , Civil calendar , - , Burmese Era ( Culāsakaraj) , 22 March 638 , Civil calendar The tradition of using different reference calendars continued in Siam in 1912 when King

Vajiravudh Vajiravudh (1 January 188126 November 1925) was the sixth Monarchy of Thailand, king of Siam from the Chakri dynasty, titled Rama VI. He reigned from 1910 until his death in 1925. King Vajiravudh is best known for his efforts to create and pro ...

decreed that the Buddhist Era would now track the

, the Siamese version of the

with the New Year's Day of 1 April. Therefore, the Thai Buddhist Era year of 2455 began on 1 April 1912 (as opposed to 15 April 1912 according to the lunisolar calendarEade 1989: 166). The Thai Buddhist Era was further realigned to the Gregorian calendar on 6 September 1940 when Prime Minister Phibunsongkhram decreed 1 January 1941 as the start of the year 2484 BE. As a result, the Year 2483 was only 9 months long, and the Thai Buddhist Era equals that of the

plus 543 years.

Current usage

The lunisolar calendar is used to mark important Buddhist holidays. Many of the holidays are celebrated as public holidays. {, class="wikitable" , - ! width="200", Buddhist calendar date ! width="100", International date ! width="300", Public holiday in ! width="300", Notes , - , Full moon of Phussa , January , Sri Lanka , Duruthu Poya: Commemorates the first visit of the Buddha to Sri Lanka , - , Full moon of Māgha , February , Cambodia, Laos, Sri Lanka, Thailand , Magha Puja in Cambodia, Laos, Thailand and known as Navam Poya in Sri Lanka , - , Full moon of Phagguṇa , March , Laos, Myanmar, Sri Lanka , Boun Pha Vet (Laos), Tabaung Festival (Myanmar), Medin Poya (Sri Lanka) , - , Almost always in Citta, sometimes in Vesākha , 13–17 April
(varies by country) , Cambodia, Laos, Myanmar, Sri Lanka, Thailand , Songkran (Southeast Asian New Year)
Traditionally, the New Year's Day is marked when the Sun enters Aries but the day is now fixed in most countries; Myanmar still follows the tradition. It also marks the beginning of the next Buddhist calendar animal zodiac year for certain countries. , - , Full moon of Citta , April , Sri Lanka , Bak Poya: Commemorates the second visit of the Buddha to Sri Lanka , - , Full moon of Vesākha , May , Cambodia, Laos, Thailand, Sri Lanka, Myanmar, Malaysia, Singapore , Buddha Day (

Vesak Vesak (; Sanskrit: '), also known as Buddha Jayanti, Buddha Purnima, Visak Bochea and Buddha Day, is a holiday traditionally observed by Buddhism, Buddhists in South Asia and Southeast Asia, as well as in Tibet and Mongolia. It is among the ...

) , - , Full moon of Jeṭṭha , June , Sri Lanka , Poson Poya: Commemorates introduction of Buddhism to Sri Lanka , - , Full moon of Āsāḷha , July , Cambodia, Laos, Myanmar, Thailand, Sri Lanka ,

Vassa ''Vassa'' (, , both "rain") is the three-month annual retreat observed by Theravada Buddhists. Taking place during the wet season, Vassa lasts for three lunar months, usually from July (the Burmese month of Waso, ) to October (the Burmese ...

Esala Poya (Sri Lanka)

Asalha Puja Āsāḷha Pūjā () is a Theravada Buddhist festival which typically takes place in July, on the full moon of the Āsādha month. It is celebrated in Indonesia, Cambodia (), Thailand, Sri Lanka, Laos, Myanmar and in other countries with Ther ...

(Thailand) , - , Full moon of Sāvaṇa , August , Sri Lanka , Nikini Poya , - , Full moon of Poṭṭhapāda , September , Laos, Sri Lanka , Binara Poya (Sri Lanka) , - , Full moon of Assayuja , October , Cambodia, Laos, Myanmar, Sri Lanka , End of Vassa
Boun Suang Huea (Laos);

Thadingyut Festival The Thadingyut Festival (), also known as the Lighting Festival of Myanmar, is held on the full moon day of the Burmese lunar month of Thadingyut. As a custom, it is held at the end of the Buddhist sabbath (Vassa) and is the second most popular f ...

(Myanmar); Vap Poya (Sri Lanka); Wan Ok Phansa (Thailand) , - , Full moon of Kattika , November , Laos, Myanmar, Sri Lanka, Thailand, Cambodia , That Luang Festival (Laos);

Tazaungdaing Festival The Tazaungdaing Festival (, also known as the Festival of Lights and spelt Tazaungdine Festival), held on the full moon day of Tazaungmon, the eighth month of the Burmese calendar, is celebrated as a national holiday in Myanmar and marks the e ...

(Myanmar); Il Poya (Sri Lanka);

Loi Krathong Loy Krathong (, , ) is a Thai festival celebrated annually throughout Kingdom of Thailand, Thailand and in nearby countries with significant Southwestern Tai languages, South Western Tai cultures (Laos, Shan State, Shan, Mon State, Mon, Tanintha ...

(Thailand); Bon Om Touk (Cambodia) , - , Full moon of Māgasira , December , Sri Lanka , Undhuvap Poya (Sri Lanka)

Computer support

The Thai-style "Buddhist calendar", which is the Gregorian calendar with the Buddhist era, is supported in

Java 8 The Java language has undergone several changes since JDK 1.0 as well as numerous additions of classes and packages to the standard library. Since J2SE 1.4, the evolution of the Java language has been governed by the Java Community P ...

iOS Ios, Io or Nio (, ; ; locally Nios, Νιός) is a Greek island in the Cyclades group in the Aegean Sea. Ios is a hilly island with cliffs down to the sea on most sides. It is situated halfway between Naxos and Santorini. It is about long an ...

, and

macOS macOS, previously OS X and originally Mac OS X, is a Unix, Unix-based operating system developed and marketed by Apple Inc., Apple since 2001. It is the current operating system for Apple's Mac (computer), Mac computers. With ...

Notes

References

Bibliography

* * * * * * * * * * * {{Buddhism topics * Calendar eras Specific calendars