Buddhist calendar

The Buddhist calendar is a set of lunisolar calendars primarily used in Tibet, Cambodia, Laos, Myanmar, Bangladesh, India, Sri Lanka, Thailand and Vietnam as well as in Malaysia and Singapore 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.

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.

The Burmese calendar in turn was based on the "original" Surya Siddhanta system of ancient India (believed to be Ardharatrika school).

[2] In all Theravada traditions,the calendar's epochal year 0 date was the day in which the Buddha attained parinibbāna.

In Burmese Buddhist tradition, it was 13 May 554 BCE (Tuesday, Full moon of Kason 148 Anjanasakaraj).

[5] The Synodic months are used to compose the years while the 27 lunar sidereal days (Sanskrit: nakshatra), alongside the 12 signs of the zodiac, are used for astrological calculations.

[6] (The Burmese calendar also recognizes a solar month called Thuriya Matha, which is defined as 1/12th of a year.

Because of the inaccuracy of the calendrical calculation systems, the mean and real (true) New Moons rarely coincide.

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 Cambodian, Lao and Thai lunisolar calendars use a slightly different method to place the intercalary day.

[13] Thailand and Cambodia no longer use the traditional lunisolar calendar to mark the New Year's Day.

The Cambodian, Lao and Thai systems give animal names to the years from a cycle of 12.

[citation needed] 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).

In Myanmar, Burmese calendarists have tried to deal with the issue by periodically modifying the intercalation schedule in the Metonic cycle.

[note 2] The Buddhist Era was first introduced to Southeast Asia along with Buddhism in the early centuries CE.

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.