Buddhist Calendar - Year Numbering

Year Numbering

The numbered year coincides with the sidereal year containing twelve zodiacal signs (rasi) so it can begin on any date from 6 Caitra/Tagu to 5 Vaisakha/Kason, meaning the rest of the month will be in an adjacent year. Thus any particular numbered year may be missing some days of the month while an adjacent year has the same set of dates at both its beginning and end.

Four eras were/are used:

• Anchansakarat, from 10 March 691 BC (rarely used),
• Buddhasakarat, Buddhist Era or BE, from 11 March 545 BC, believed to be the date of the death of the Buddha. (BE–AD of 544 used to be common, but BE–AD is now 543 in Thailand, beginning after April before 1940, then began and still begins 1 January),
• Mahasakarat from 17 March 78 (same as the Saka Era in India, used in Thailand until the mid-13th century, standard in Cambodia),
• Chulasakarat from 22 March 638 (adopted in Thailand mid-13th century, standard in Burma).

All years are elapsed/expired/complete years, thus their epochal year is year 0, not year 1, because a complete year had not yet elapsed during it. The epochal dates only apply to year 0 — modern dates for the entry of the Sun into the first rasi (the beginning of the sidereal year) occur later in the Gregorian calendar due to precession of the equinoxes. The calculations do not begin with zero at epoch — instead an offset of a certain number of whole and fractional days, which can amount to more than one year, must be added to all calculations, explaining the apparent Buddhasakarat inconsistency. Here 544 has an offset of 4 days at epoch whereas 543 has an offset of 369 days.