Chhat Puja is celebrated twice a year: once in the summers (May-July), called the Chaiti Chhath, and once in the winters (September-November) around a week after Deepawali (Diwali), called the Kartik Chhath. The latter is more popular because winters are the usual festive season in North India, and Chhath being an arduous observance, requiring the worshippers to fast without water for more than 24 hours, is easier to undertake in the Indian winters.
Because Chhath is mainly a Bihar festival, wherever people from Bihar have migrated, they have taken with them the tradition of Chhath. This is a ritual bathing festival that follows a period of abstinence and ritual segregation of the worshiper from the main household for four days. During this period, the worshiper observes ritual purity, and sleeps on the floor on a single blanket. The main worshipers, called Parvaitin (from Sanskrit parv, meaning 'occasion' or 'festival'), are usually women.