DateThe solar calendar in everyday use
Thailand’s civil solar calendar uses Gregorian-style months and leap days with Buddhist Era year numbering. It is the system used for everyday dates such as schedules and document dates. The official civil year has begun on January 1 since 1941.
The lunar calendar and observances
Thailand also observes a lunisolar calendar. Its months follow the phases of the Moon, with adjustments to keep the lunar year in step with the seasons. Observances such as Visakha Bucha and Loy Krathong follow lunar dates, so their Gregorian dates can change from one year to the next.
Identify the kind of date first
A date written with an ordinary civil month can go into the Thai date converter. A date specified by a waxing or waning lunar day needs a lunar calendar for the relevant year. Changing the year number alone does not convert a lunar date to a solar date.
For the shift from April to January, see the Thai Fine Arts Department’s calendar history.