Lunar month with the Sun one or two days before that evening ("e.g.", in the Islamic calendar). In ancient Egypt the lunar month began on the day when the waning moon could no longer be seen just before sunrise. Others use calculation, of varying degrees of sophistication, "e.g.", the Hebrew calendar or the ecclesiastical lunar calendar. Yet others run from full moon to full moon. Calendars count integer days, so months may be 29 or 30 days in length, in some regular or irregular sequence. In India the month from conjunction to conjunction is divided into thirty parts known as "tithis". The
Adhik Maas Puruśottama Māsa, it is said that the name was given by Lord Vishnu as his name to this month. The solar year is made up of 365 days and about 6 hours, and the lunar year is made up of 354 days. Thus there is a gap of 11 days, 1 hour, 31 minutes and 12 seconds between the lunar and the solar years. As this gap accumulates each year, it approximates in three years to one month. No "adhik mas" falls during Margsheersh to Magh. A case of Adhik Karttik is extremely rare, but in the 250-year span (1901-2150