Lunar calendar traces of its origin in the earlier lunar calendar, which continued to be used alongside it for religious and agricultural purposes. Present-day lunisolar calendars include the Chinese, Hindu, and Thai calendars. Synodic months are 29 or 30 days in length, making a lunar year of 12 months about 11 days shorter than a solar year. Some lunar calendars do not use intercalation, such as most Islamic calendars. For those that do, such as the Hebrew calendar, the most common form of intercalation is to add an additional month every second or third year. Some lunisolar calendars are also calibrated by
Lunar month Lunar month In lunar calendars, a lunar month is the time between two successive syzygies (new moons or full moons). The use of the lunar month varies by which culture has utilized the method, the main difference being when the "new" month begins. This article deals with the definitions of a 'month' that are mainly of significance in astronomy. For other definitions, including a description of a month in the calendars of different cultures around the world, see: month. In Shona, Middle-Eastern, and European traditions, the month starts when the young crescent moon becomes first visible at evening after conjunction