Drik and Vakya: why two panchangams disagree

One computes where the Moon actually is; the other uses mean-motion tables in verse. On the same day they can differ by hours.

If the almanac on your wall and the app in your pocket disagree, this is almost always why. They are not the same system, and neither one is a corrupted version of the other.

Vakya

Vakya computes positions from mean-motion tables encoded as verses — mnemonic sentences that give the Moon's longitude without an ephemeris. It is old, it is portable, and it was designed to be carried in memory.

The Pambu Panchangam, printed by Manonmani Vilasam Press in Chennai since 1883 and known by the snake on its cover, is the vakya almanac most Tamil families keep.

Drik

Drik means seen. It computes true positions, which is why it matches eclipses and conjunctions. The Thirukanitha panchangam is the drik almanac; it is what the Tamil Nadu government calendar uses, and what nearly every app and website computes.

How far apart they get

Tithi and nakshatra ending times are where it shows first. Differences of 6 hours 48 minutes are documented, and Drik Panchang puts the outer bound at around twelve hours.

The larger effect is on slow planets. When a retrograde straddles a sign boundary the two systems can place a transit weeks apart: Sani peyarchi was 19 December 2017 by vakya and 26 January 2017 by thirukanitha — thirty-eight days.

One correction while we are here. A figure of 43 minutes for 21 June 2020 circulates on forums. It does not reproduce: the conjunction computes to 12:11 IST against vakya's 12:30, which is nineteen minutes.

Who follows which

Major Vaishnava temples — Srirangam, Kanchi Varadaraja — and many Sri Vaishnava households keep vakya. Shaiva mutts and most modern almanacs use thirukanitha.

The practical trap: a household may keep the Pambu for festivals and a thirukanitha app for timings, and never notice the mismatch. Tamil month start, ekadashi, pradosham and above all the peyarchi dates can all land on different days.

Which is right

Drik matches the sky. That is a statement about astronomy, not about which almanac your family should keep — a tradition that has kept vakya for generations is not making an error of observation, and telling them so would miss what the question is about.

What a panchangam owes you is to say which basis it used. We compute drik, and we say so on every page.