Tibetan calendar
The Tibetan calendar (Tibetan: ལོ་ཐོ, Wylie: lo-tho), or the Phukpa calendar, known as the Tibetan lunar calendar, is a lunisolar calendar composed of either 12 or 13 lunar months, each beginning and ending with a new moon. A thirteenth month is added every two or three years, so that an average Tibetan year is equal to the solar year.