Methodology

The short version

Every panchangam value on this site is computed live from the Swiss Ephemeris (Astrodienst) using Lahiri (Chitrapaksha) Ayanamsa and the Drik Ganita (observational / true) calculation method. Matches the Rashtriya Panchang published by the Positional Astronomy Centre, Kolkata.

Ayanamsa

Lahiri = the official ayanamsa of the Government of India (adopted 1955). Chitrapaksha means the ayanamsa is calibrated so that the star Chitra (Spica) sits at exactly 180° 00' 00" of the sidereal zodiac. We do not offer Surya Siddhanta / Ramnark / Krishnamurti alternates on the primary pages because they diverge from the Rashtriya Panchang; if you need one of them, use the raw ephemeris values as a starting point.

Calculation method: Drik Ganita vs Surya Siddhanta

We use Drik Ganita (based on observed planetary positions) rather than Surya Siddhanta (based on medieval mean-motion tables). Drik Ganita matches modern astronomical reality; Surya Siddhanta can be off by hours on planetary positions — critical for muhurtam and tithi boundaries.

City coordinates

Sunrise, sunset, and every derived value (rahu kalam, yamagandam, choghadiya, muhurtam windows) are city-specific. We use IANA timezone data + GeoNames coordinates for 40+ cities. If the coordinates for your city look off (large delta from local reality), report via Corrections.

Sunrise convention

Center-of-disk sunrise at sea level, refraction-corrected. Some traditional panchangs use "upper limb" sunrise (edge of disk touching horizon) which differs by ~2 minutes. Adjust muhurtam start-times accordingly if your family paddhati specifies upper-limb.

Precision & limitations

• Tithi boundaries: precise to the second based on true lunar longitude minus true solar longitude / 12°.
• Nakshatra: precise to the second based on true lunar longitude / (13° 20').
• Sunrise / sunset: ±30 seconds vs USNO tables (atmospheric refraction model dependent).
• Rahu / Yamagandam / Gulika: derived from an eightfold day-length division; matches Muhurta Chintamani convention.
• Festival dates: sensitive to which panchangam authority determines tithi vyapti (Udaya Tithi vs Purnimanta / Amavasyanta convention). We follow the Udaya Tithi + Chandramana convention for South Indian festivals unless the festival explicitly uses a different rule (e.g., Vaikuntha Ekadashi = Sukla Ekadashi of Margashira in Dhanurmasa).

Cross-verification

Before every major festival ship, dates are cross-verified against DrikPanchang + at least one temple portal (TTD, ISKCON, or the regional Adhikari). If the site's engine and external sources disagree, we investigate the difference (usually a convention question, not a calculation error).

Open engine

The panchangam engine (/_next/static/chunks/panchangam-engine.js) runs client-side; you can inspect it via browser dev tools. Bug reports welcome via Contact.