It takes place in November/December during the full moon day of Thinlā (थिंला), the second month in the lunar Nepal Era calendar.

A yomari is a confection of rice flour (from the new harvest) dough shaped like fish and filled with brown cane sugar and sesame seeds, which is then steamed.

On this full moon day, people of the Kathmandu Valley offer worship to Annapurna, the goddess of grains, for the rice harvest.

Sacred masked dances are performed in the villages of Hari Siddhi and Thecho at the southern end of the Valley to mark the festival.

According to Basu Pasa's historical book Kantipur, among different shapes yomari, 'Bayo' symbolizes the male sexual organ whereas the triangle shaped with two points at the end known as 'Mayo' yomari suggests the female sexual organ and represents father and mother respectively.