01What Sharad Purnima is
Sharad Purnima is the Purnima of Ashwin, the first full moon after the monsoon, when the air is clear and the moon is held to be at its brightest of the year. The tradition says it is the one night the Moon shines with all sixteen of its kalas, and that its light carries amrit, a nourishing essence, into whatever is left beneath it. In Bengal, Odisha and Assam it is Kojagari Lakshmi Puja; in Odisha it is also Kumar Purnima; in Braj it is the night of the raas. It closes the season of rains and opens the month of Kartik.
02The story told of it
Two accounts belong to this night. The first is Lakshmi's: the tradition tells that she moves across the earth on the full moon of Ashwin asking Ko jagarti, who is awake, and favours the homes she finds awake and lit. Kojagari, the name used in the east, comes from that question. The second is Krishna's. The Bhagavata Purana describes the night of the maharaas, when Krishna played his flute on the bank of the Yamuna under the autumn moon and the gopis of Vrindavan left their homes to dance with him, each of them feeling he danced with her alone.
03How it is kept
The best known custom is the kheer: rice cooked slowly in milk with sugar, set out in the open under the moonlight after moonrise, covered with a fine cloth, and eaten the next morning as prasad. The tradition holds that the light of the moon passes into it. Families who keep Kojagari stay awake through the night, play games and sing, and worship Lakshmi with lamps at the door. Many fast through the day and break the fast after offering water to the risen moon. Krishna temples hold raas and kirtan, and in Braj the night is given to song.
04How the day is chosen
It is kept on the day its tithi is current at sunrise in your city, or for a night festival, at sunset.
05Sharad Purnima in other years