In the Rigveda, hymns to Surya (the sun god) and to Usha (the dawn goddess) are among the oldest compositions in any Indian language. The practice of standing in water to offer prayers to the sun — Surya Arghya — is mentioned in the Atharva Veda. Chhath, in its folk form, preserves this Vedic solar worship in what may be its oldest surviving community practice.

The Mahabharata connection is through Karna — one of the most compelling figures in the entire epic. Karna was the son of Kunti and Surya, the sun god. He was born bearing golden armour and earrings, gifts of his divine father. He grew up not knowing who his father was, given away as a newborn, raised by a charioteer's family. But he worshipped Surya every day, standing in water, facing the sun, offering Arghya — exactly as Chhath is performed. He was so devoted to this practice that he gave away whatever he owned to anyone who asked during his Surya Arghya — which is how Indra was able to trick him out of his armour.

Draupadi is also connected to Chhath mythology. During the Pandavas' years of exile in the forest, when provisions were running out, sage Dhaumya suggested she perform Chhath to invoke the blessings of Surya for the family's survival. She observed the fast and performed the ritual, and provisions came. This story establishes Chhath as both a festival of survival and a demonstration of the discipline that makes survival possible.

Historically, Chhath is most strongly rooted in the Mithila and Bhojpur regions — what is today Bihar, Jharkhand, and eastern Uttar Pradesh. From there, it travelled with migrating communities to every city in India and eventually to Trinidad, Mauritius, Fiji, Suriname, and wherever people from these regions settled globally.

Day 1 — Nahay Khay (November 12): The Vrati (fasting devotee) takes a bath in a sacred river, brings home holy water, and cooks one pure meal using this water. The meal is eaten once, after the family has eaten. From this point the kitchen maintains strict purity — no onion, no garlic, no non-vegetarian food — until the festival ends.

Day 2 — Kharna (November 13): A full day's fast, broken after sunset with a specific prasad: Rasiyaav (kheer made with rice, milk, and jaggery or sugarcane juice) and roti made from rice flour or wheat. After the Kharna meal, the waterless fast begins — no food, no water for the next 36 hours.

Day 3 — Sandhya Arghya (November 14): The main Chhath ritual. The Vrati goes to the river or water body in the late afternoon, stands in the water, and offers Arghya to the setting sun as it descends toward the horizon. Bamboo baskets (sup) filled with fruits, Thekua, sugarcane, and other offerings are held above the water. The sun is offered milk and water. The vigil continues through the night at the ghat.

Day 4 — Usha Arghya (November 15): Before dawn, the Vrati returns to the water and offers Arghya to the rising sun. As the sun clears the horizon, the fast is broken with the Prasad — primarily Thekua and fruits. The fast has lasted 36 hours without a drop of water.