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
Adhik Maas "adhika"; "maal", "māla"; "maas", "maasa", "mās", "māsa", "mas", "mass". This is the thirteenth month of the lunar calendar. Adhik Maas adopts the name of the month that follows. Purushottam Maas is considered inauspicious and no activities like weddings or moving into a new house are conducted. It is a time for prayer, fasting, charity, and self-improvement. According to "Vasishtha Siddhantha" (the treatise of Vasishtha), Purushottam Maas or the extra lunar month occurs after every 32 months, 16 days and 8 "ghati". (A "ghati" is th of a sidereal day, approximately 24 minutes, so 8 "ghati" is about 3 hours.) In