Chhath puja is performed on Kartik Shukala Shashti, which is the sixth day of the month of Kartik in the Hindu Calendar. This falls typically in the month of October or November in the Gregorian Calendar.

It is also celebrated in the summer (March–April), on Chaitra Shashti, some days after Holi; this event is called Chaiti Chhath. The former is more popular because winter is the usual festive season in North India, and Chhath, being an arduous observance, requiring the worshipers to fast without water for around 36 hours continuously, is easier to undertake in the Indian winters.