New moon western horizon shortly after sunset and before moonset. A lunation or synodic month is the average time from one new moon to the next. In the J2000.0 epoch, the average length of a lunation is 29.530588 days (or 29 days, 12 hours, 44 minutes, and 2.8 seconds). However, the length of any one synodic month can vary from 29.26 to 29.80 days due to the perturbing effects of the Sun's gravity on the Moon's eccentric orbit. In a lunar calendar, each month corresponds to a lunation. Each lunar cycle can be assigned a unique lunation number to identify it. The
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