If you compare two reputable Panchangs you will sometimes see a nakshatra ending at 10:41 in one and 10:42 in the other, or a Sankranti several minutes apart. Neither is necessarily wrong. The differences usually come from a handful of well-understood choices.

Sidereal, tropical and precession

Western astrology uses the tropical zodiac, measured from the spring equinox. Indian Jyotish uses the sidereal zodiac, anchored to the fixed stars. The Earth's axis slowly wobbles (precession), so the equinox point drifts backwards against the stars by about 50.3 arc-seconds per year. The accumulated gap between the two zodiacs is the ayanamsa.

Different ayanamsas

The exact starting point of the sidereal zodiac is a convention:

  • Lahiri (Chitrapaksha), adopted by the Indian Calendar Reform Committee in 1956, places the star Chitra (Spica) opposite 0° Mesha. Its value is about 24°12′ in 2025. It is the most widely used in India.
  • Raman (B. V. Raman) and Krishnamurti (KP) use slightly different starting values.

Why Panchangs differ by minutes

  1. Ayanamsa variants. Even within "Lahiri" there are small variants. The effect depends on the body's speed: a 24″ difference shifts a Sankranti by roughly 10 minutes (the Sun moves about 1° a day) but a Moon-based nakshatra end by under a minute (the Moon moves about 13° a day).
  2. Sunrise definition. Modern drik Panchangs use the moment the Sun's upper limb appears, with atmospheric refraction; some use the centre of the disc. This moves sunrise by a minute or two, and with it Rahu Kaal, muhurtas and the udaya tithi.
  3. Coordinates and elevation. Sunrise differs across a single city, and elevation changes the visible horizon.
  4. Astronomical models. Different ephemerides and delta-T estimates produce small differences in positions.
  5. Conventions. Udaya-tithi rules, Amanta or Purnimanta months, and festival tie-breaks can shift a displayed date, even when the astronomy agrees.

Traditions vary by region and Panchang convention.

Profiles on this platform

Every result is produced under a named calculation profile. The default profiles use the standard Lahiri ayanamsa (with nutation) and sunrise by the refracted upper limb. A separate DrikPanchang-compatible profile uses an empirically calibrated Lahiri variant (the standard value offset by about 22″ and applied without nutation) that reproduces DrikPanchang.com Sankranti and Yoga timings to about a minute; it is a compatibility mode, not an official definition. Details are in the methodology; see also Sankranti and Makar Sankranti.