The Chhath Puja - Worship of the Sun God

Chhath is an ancient Hindu festival dedicated to Surya, the Hindu Sun God. The 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. The Chhath Puja is performed in order to thank Surya for sustaining life on earth and to request the granting of certain wishes. The Sun, considered the god of energy and of the life-force, is worshiped during the Chhath fesival to promote well-being, prosperity and progress. In Hindu mythology, Sun worship is believed to help cure a variety of diseases, including leprosy, and helps ensure the longevity and prosperity of family members, friends, and elders.
It is believed that the ritual of Chhath puja may even predate the ancient Vedas texts, as the Rigveda contains hymns worshiping the Sun god and describes similar rituals. The rituals also find reference in the Sanskrit epic poem Mahābhārata in which Draupadi is depicted as observing similar rites. It is also believed that Chhath was started by Karna, the son of Surya Putra Karna who ruled over the Anga Desh (present day Bhagalpur district of Bihar) during the Mahabharat Age. He was a great warrior and fought against the Pandavas in the Kurukshetra War.
Its yogic/scientific history dates back to the Vedic times. The rishis of yore used this method to remain without any external intake of food as they were able to obtain energy directly from the sun's rays. This was done through the Chhath method.
The word chhath denotes the number 6 in Hindi and the festival is celebrated on the sixth day of the Hindu lunar month of Kartik. The word Chhath is also a compound of two words: "Chah" meaning "six stages", and "Hath" refers to the science of Hath Yog (austerity). The word Chhath refers to the process of consciously obtaining the solar energy through six stages involving the methods of Hath Yog. "Hath" here refers to the austerities such as fasting and standing in water.

The rituals of the festival are rigorous and are observed over a period of four days. They include holy bathing, fasting and abstaining from drinking water (Vratta), standing in water for long periods of time, and offering prashad (prayer offerings) and arghya to the setting and rising sun. Chhath 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.This is the only holy festival which has no involvement of any pandit (priest). The devotees offer their prayers to the setting sun and then the rising sun in celebrating its glory as the cycle of birth starts with death. It is seen as the most glorious form of Sun worship.
The Chhath Puja is celebrated primarily in Bihar, Jharkhand and the Terai regions of Nepal, and is more prevalent in areas where migrants from those areas have a presence.  It is also celebrated in all regions and major urban centers in India. This festival is celebrated in the regions including but not exclusive to the northeast region of India, Madhya Pradesh, Andhra Pradesh, Uttar Pradesh, Chhattisgarh, Tamil Nadu, Chandigarh, Gujarat, Delhi, Mumbai and Mauritius.

Om Shree Bhaskaray Namah !
Blessed Be !