The Suriyakati calendar ( Thai : ปฏิทิน สุริยคติ ไทย , also: Thai sun calendar ) is the calendar system currently used in Thailand . It is based on the world's most widely used Gregorian calendar , but uses the Buddhist calendar (BE) to count the years . This means that the years are 543 larger than in the Christian calendar .
The calendar was introduced by King Chulalongkorn (Rama V) in 1888, with New Year's Day falling on April 1st of the respective year. In 1941 (2484 BE), the then Thai Prime Minister Phibul Songkhram moved New Year's Day to January 1, so that the year 2483 BE was only nine months long.
Calendars in Thailand today include both calendar systems for convenience. The year according to the Buddhist calendar is written in Thai numerals , while the Gregorian year is given in both Arabic and Chinese numerals .