33 festivals, each dated from the Moon rather than from last year’s calendar — and each showing the rule that decides it.
A tithi is not a day. It begins and ends at a real minute and can start at any hour, so naming the tithi does not name the date — you also need the moment of the day that decides. There are five, and they are not interchangeable.
the tithi that is running when the sun comes up
the fourth of five equal parts of daylight
the hour and a half following sunset
the middle of the night
the middle of the daylight hours
Diwali is the clearest case. On 8 November 2026 the tithi at sunrise is Chaturdashi and the tithi at sunset is Amavasya; Lakshmi Puja is performed at pradosh, so the date is the 8th. Read the same tithi at sunrise and you get the 9th.
Cast a free kundli, or ask any of 24 astrologers what this year actually holds for you. Billed by the minute, and only while somebody is answering.