Learn · Panchang & muhurta

What is Tithi?

A tithi is a lunar day: the interval during which the Moon moves 12° further ahead of the Sun. It is the first and most important limb of the panchang, and the anchor for almost every Hindu festival and vrat.

SUNEARTHAmavasya · 30Shukla 8Purnima · 15Krishna 8Shukla paksha — the Moon draws away from the SunKrishna paksha — it closes back in30TITHIS IN A MONTH12° of separation each19–26 hONE TITHI LASTSthe Moon’s speed varies
A tithi is 12° of the Moon’s lead over the Sun; thirty of them make the lunar month, fifteen waxing and fifteen waning.
In a lunar month30 — 15 waxing, 15 waning
One tithi12° of the Moon’s lead over the Sun
Lastsabout 19 to 26 hours
NamedPratipada … Purnima, Pratipada … Amavasya

The 30 tithis

One synodic (lunar) month contains 30 tithis. The first 15, while the Moon waxes, form the Shukla Paksha (Pratipada, Dwitiya … up to Purnima, the full moon). The next 15, as the Moon wanes, form the Krishna Paksha, ending in Amavasya (new moon).

Why a tithi isn’t 24 hours

Because the Moon’s speed varies along its elliptical orbit, a tithi is not fixed — it ranges from about 19 to 26 hours. So a tithi can occasionally skip a sunrise (kshaya) or span two (vriddhi). The tithi “in force” on a day is usually the one running at sunrise.

Tithi and festivals

Festivals are defined by tithi, not by the Gregorian date — Janmashtami is Shravana Krishna Ashtami, Diwali is Ashwin Krishna Amavasya. This is why their English dates move every year.

Related

Today’s Tithi Festival dates

Questions

How many tithis are there?

30 per lunar month — 15 in the waxing Shukla Paksha and 15 in the waning Krishna Paksha.

Why does a tithi’s length vary?

Because the Moon travels at different speeds along its elliptical orbit, the time to gain 12° on the Sun varies from roughly 19 to 26 hours.