Lunar month circular, the speed of Earth's progression around the Sun varies during the year. Thus, the angular rate is faster nearer periapsis and slower near apoapsis. The same is so for the Moon's orbit around the Earth. Because of these variations in angular rate, the actual time between lunations may vary from about 29.18 to about 29.93 days. The long-term average duration is days (29 d 12 h 44 min 2.8016 s). The synodic month is used to calculate eclipse cycles. It is customary to specify positions of celestial bodies with respect to the vernal equinox. Because of Earth's precession of
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