Agrahayana

Agrahayana or Margashirsha is the ninth month of the Hindu lunar calendar and the Indian national calendar. The name of the month is derived from the position of the Moon near the Mrigashīrsha nakshatra (star) on the full moon day. The month corresponds to the beginning of the pre-winter (Hemanta) season and falls in November–December of the Gregorian calendar.

In the Hindu solar calendar, it corresponds to the month of Vṛścika and begins with the Sun's entry into Scorpio. It corresponds to Ogrohayon, the eighth month in the Bengali calendar. In the Tamil calendar, it corresponds to the ninth month of Margazhi, falling in the Gregorian months of December–January. In the Vaishnava calendar, it corresponds to the ninth month of Kesava.

In the Hindu lunar calendar, each month has 29 or 30 days. The month begins on the next day after Amavasya (new moon) or Purnima (full moon) as per amanta and purnimanta systems respectively. A month consists of two cycles of 15 days each, Shukla Paksha (waning moon) and Krishna Paksha (waxing moon). Days in each cycle is labeled as a thithi, with each thithi repeating twice in a month.