This is their culture. Chhath festival is celebrated with great pomp in Bihar. This festival is the only festival of Bihar or entire India which has been going on since the Vedic period and now it has become the culture of Bihar. This festival shows a small glimpse of the Vedic Aryan culture of Bihar. This festival is celebrated according to Sun worship and Usha worship and Arya tradition as described in Rigveda.
In Bihar, this festival is celebrated by Hindus and followers of other religions including Islam are also seen celebrating it. Gradually this festival has become popular among the diaspora as well as across the world. Chhath Puja is dedicated to Sun, Nature, Water, Air and her sister Chhathi Maiya to thank the deities for restoring life on earth, Chhathi Maiya, also known as Runbe Maiya in Mithila, in Bhojpuri she is called Sabita Mai and in Bengali she is called Ranbe Thakur. Chhathi Maiya, the sixth form of Parvati, sister of Lord Surya, is worshiped as the goddess of the festival. Chhath is celebrated six days after Kali Puja on the sixth lunar day. During Chhath in Mithila, Maithil women wear pure cotton dhoti without stitching to depict the pure traditional culture of Mithila.
The rituals of the festival are rigorous and are celebrated over a period of four days. These include holy bathing, fasting and abstinence from drinking water (vritta), standing in water for long periods of time, and offering prasad (prayer offerings) and arghya. The main worshipers, called Parvatin (from Sanskrit parva, meaning ‘occasion’ or ‘festival’) are usually women. However, a large number of men also observe this festival as Chhath is not a gender-specific festival. Everyone, men, women, old and young, observe the fast of Chhath Mahaparva. Some devotees also perform a procession march as they head for the river banks.