Thai solar calendar

The months and days of the week are the same as those used in the Western calendar, only their names differ. The year however is counted from the Buddhist Era (B.E.), which is 543 years earlier than the Christian era (A.D.). For example, 2003 A.D. is equivalent to 2546 B.E. The era is based on the death of Gautama Buddha, which is dated to 543 BC by the Thai.

Until 1888 Thailand used a lunar calendar, in which the date of the New Year (Songkran) was between April 13 and 15. The new calendar, decreed by King Chulalongkorn (Rama V), was called Ratanakosinsok, and was nearly identical with the western gregorian calendar. However the New Year date was fixed to April 1, and the year numbering started at the founding of Bangkok, 1781. King Vajiravudh[?] (Rama VI) changed the year counting to Buddhist Era in 1912.

In 1940 Prime Minister Pibunsongkram changed the official New Year to January 1. Now both New Year's days are public holidays. The buddhist feasts are still calculated according to the lunar calendar, so they change their date in the solar calendar every year.