The Thai Buddhist Era and Western Years

Two Year Counts

Thailand writes official dates in the Buddhist Era, พุทธศักราช, abbreviated พ.ศ. (B.E.). The Western year count is คริสต์ศักราช, ค.ศ. (A.D. or C.E.). Months and days are the same in both: 11 October 2026 is written 11 ตุลาคม 2569 in Thai. Only the year number differs.

Since 1 January 1941 the Thai year and the Western year begin on the same day, so the rule is simple:

• B.E. = A.D. + 543, for example 2026 + 543 = 2569.
• A.D. = B.E. − 543, for example 2500 − 543 = 1957.

When the Thai Year Began

The Thai new year moved to 1 January only in 1941. According to the National Library of Thailand, it followed the lunar calendar until R.S. 108 (B.E. 2432, 1889), when the first day of the fifth lunar month fell on 1 April and King Chulalongkorn made 1 April New Year's Day. From B.E. 2484 the government of Field Marshal Plaek Phibunsongkhram moved New Year's Day to 1 January, to match the international calendar.

Each Buddhist year from 2432 to 2482 ran from 1 April to 31 March. Its January, February and March fell in the next Western year, which is why those months are only 542 years apart: 15 January 1939 was in B.E. 2481, not 2482.

The Year With Nine Months

To move New Year's Day without skipping a number, B.E. 2483 began on 1 April 1940 as usual but ended on 31 December 1940, and B.E. 2484 began on 1 January 1941. The Fine Arts Department and the National Library describe B.E. 2483 as a year of only nine months.

So there was no January, February or March 2483. A date written as 1 กุมภาพันธ์ 2483 is either a mistake or a date counted the modern way afterwards; the converter reports it as a date that did not exist.

Reading Dates in Old Documents

• For a date from April to December, add or subtract 543, as today.
• For a date from January to March before 1941, use 542: a birth on 10 February 1938 was registered in B.E. 2480. Someone who later converts that date by adding 543 gets 2481, one year too many.
• Many date libraries and spreadsheets turn a Western date into a Buddhist year by adding 543 to every date. Their results for January to March before 1941 differ from the documents of that time.
• Thai documents sometimes use Thai digits: ๒๕๖๙ is 2569.

R.S. and Other Year Counts

Before the Buddhist Era became the usual count, official documents also used the Rattanakosin Era, รัตนโกสินทรศก (ร.ศ., R.S.), counted from the founding of Bangkok: the National Library gives R.S. 108 as B.E. 2432. Older texts may also use the Chula Sakarat (จ.ศ.), which went with the lunar calendar. The converter handles only B.E. and A.D.

Frequently Asked Questions

Sources

Source: หอสมุดแห่งชาติ กรมศิลปากร: ศุภฤกษ์เบิกชัย สวัสดีปีใหม่ · Last checked: October 11, 2026

Source: กรมศิลปากร: ขาลนักษัตร · Last checked: October 11, 2026