It is celebrated twice a year: once in the summers, called the Chaiti Chhath, and once around a week after Deepawali, called the Kartik Chhath. The Karthik Chhath is more popular because winters are the usual festive season in North India, and fasting without water for around 42 hours or more, as required for worshippers during Chhath Puja, is easier to do in the Indian winters.

festival - chhath