Thai lunar calendar

Fortune-Telling Manual (Phrommachat) with the twelve animals of the Thai zodiac and their associated attributes, avatars and plants. Thailand, c. 1845. Chester Beatty Library

The Thai lunar calendar (Thai: ปฏิทินจันทรคติ, RTGS: patithin chanthrakhati, pronounced [pà.tì.tʰīn t͡ɕān.tʰrá(ʔ).kʰā.tìʔ], literally, Specific days according to lunar norms), or Tai calendar, is a lunisolar Buddhist calendar. It is used for calculating lunar-regulated holy days. Based on the SuriyaYatra,[clarification needed] with likely influence from the traditional Hindu Surya Siddhanta, it has its own unique structure that does not require the Surya Siddhanta to calculate. Lunisolar calendars combine lunar and solar calendars for a nominal year of 12 months. An extra day or an extra 30-day month is intercalated at irregular intervals.