How the Panchang Still Sets the Indian Festival Calendar

The Jyotisha Vedanga was composed to time yajnas, and the panchang that grew from that work still fixes the tithi of festivals in Indian public life. Natal horoscopy, the kundli of a person, came later. The cultural influence people actually live with is the five-limbed calendar: tithi, vara, nakshatra, yoga, and karana. Diwali is tied to a lunar tithi, not to a fixed civil day. Shraddha follows the fortnight. A wedding invitation that prints a nakshatra is using this limb even when nobody in the room can cast a lagna.

Festival reckoning in India follows a sidereal lunar frame. The Sun's rashi is one fact in that sky. The Moon's tithi is the one that moves most vows. Cities on Asia/Kolkata share one civil clock, UTC plus 5 hours 30 minutes, and still do not share one sunrise. Solar noon falls after 12:00 on the clock in cities well west of the old standard meridian, and before 12:00 in Kolkata and places east of it. Muhurta depends on that local sunrise. A national holiday can be one tithi while the muhurta window is a city calculation.

Wide use of the panchang does not make every yoga claim a public fact. Gajakesari is a rule about Jupiter in a kendra from the Moon. A fast on Monday is a custom for Shiva, and Monday's vara lord is the Moon. The custom and the graha meet in the calendar. They do not prove that a rashi is lucky. When Jyothish SI casts a chart it uses Lahiri ayanamsa and Swiss Ephemeris so the sidereal positions match this same family of reckoning. Interpretation of a yoga remains a textual judgment on top of that calculation. Culture explains why the tithi matters. The lagna still needs a birth time.