Chhath Puja across India

1. The date is Kartika Shukla Paksha Shashthi; the month name is the same in the Amanta and Purnimanta systems.
2. It falls on the day when this tithi prevails at local sunrise (udaya tithi).
3. If the tithi is present at two sunrises (a vriddhi tithi), the first day is taken.
4. If the tithi does not touch that period on any day (a kshaya tithi), the Hindu day on which the tithi prevails longest is used.
5. The date shown is the day of the Sandhya Arghya, offered to the setting Sun that evening; the Usha Arghya to the rising Sun follows at the next sunrise, after which the fast is broken.
6. Regional exception, inferred from the Bihar and West Bengal holiday lists of 2025 and not a documented almanac rule: when Kartika Shukla Panchami prevails at two sunrises, the Kharna is on the first of those days and the Sandhya Arghya on the second, on whose evening Shashthi prevails; the day of Shashthi at sunrise is then shown as not selected.
7. In a year with an Adhik month of the same name, it is observed in the regular (Nija) month.

Chhath spans four days: Nahay-Khay, Kharna, the Sandhya Arghya (the date shown) and the Usha Arghya next morning. The Sandhya Arghya is on the day of Kartika Shukla Shashthi at sunrise, as the Government of India almanac (Rashtriya Panchang) dates Chhath; where Shashthi prevails at two sunrises the first is taken, the only one with Shashthi at the evening Arghya. When Panchami prevails at two sunrises, the date shown is the second of them instead (27 Oct 2025 at Patna and Kolkata, the date of the Bihar and West Bengal holiday lists): a regional exception inferred from those two lists, not a documented almanac rule. The Rashtriya Panchang and the Government of India holiday list give 28 Oct 2025, the day of Shashthi at sunrise in Bihar; where the exception applies, that day is shown as not selected.

Chhath Puja