The Thai New Year is celebrated every year on 13 April to 15 April. It coincides with the New Year of many other calendars in South and Southeast Asia.
The date of the festival was originally set by astrological calculation, but it is now fixed. If these days fall on a weekend, the missed days off are taken on the weekdays immediately following.
Songkran falls in the hottest time of the year in Thailand, at the end of the dry season. Until 1888 the Thai New Year was the beginning of the year in Thailand; thereafter 1 April was used until 1940. 1 January is now the beginning of the year. The traditional Thai New Year has been a national holiday since then.