Amrutkaal What is a Tithi?
A tithi is the fundamental unit of the Hindu lunar calendar: the time the Moon takes to gain exactly 12 degrees of longitude over the Sun. Thirty tithis make one lunar month — fifteen in the waxing fortnight (Shukla Paksha) from new moon to full moon, and fifteen in the waning fortnight (Krishna Paksha) back to new moon.
The 30 tithis
Each fortnight runs: Pratipada, Dwitiya, Tritiya, Chaturthi, Panchami, Shashthi, Saptami, Ashtami, Navami, Dashami, Ekadashi, Dwadashi, Trayodashi, Chaturdashi — ending in Purnima (full moon) for the bright half and Amavasya (new moon) for the dark half. Most major observances are tithi-locked: Ganesh Chaturthi on Bhadrapada Shukla Chaturthi, Janmashtami on Bhadrapada Krishna Ashtami, Diwali on Kartika Amavasya.
Why a tithi is not a day
The Moon's orbital speed varies, so a tithi lasts anywhere from about 19 to 26 hours. This creates two regular calendar quirks: a kshaya (lost) tithi that starts and ends between two sunrises and never gets a calendar day, and an adhika (repeated) tithi that spans two sunrises and gets two. The day's "official" tithi, by convention, is the one prevailing at local sunrise — the udaya tithi.
Festival rules refine this further. Some observances follow the tithi at midday (Ganesh Chaturthi, Ram Navami), some at midnight (Janmashtami, Shivaratri), some at pradosh — the hour after sunset (Diwali's Lakshmi Puja). This is why two well-made panchangs can occasionally print different dates for the same festival: they are applying different classical conventions, not making errors.
Tithis to know
Ekadashi (11th) — the fasting day observed twice a month by devotees of Vishnu. Amavasya — new moon, the day for ancestor rites (shraddha) and Diwali. Purnima — full moon, the day of Satyanarayan puja, Holika Dahan and Raksha Bandhan. Ashtami and Navami carry both auspicious associations (Durga Ashtami) and caution for new ventures in some traditions.
Frequently Asked Questions
How is tithi calculated?
Tithi = the elongation (Moon's longitude − Sun's longitude) divided by 12°. Elongation of 0–12° is Pratipada of Shukla Paksha; 168–180° is Purnima; 348–360° is Amavasya. It is pure astronomy — any precise ephemeris yields the same result.
Why does the same tithi appear on two days sometimes?
When a long tithi covers two consecutive sunrises, both days take its name (adhika tithi). Conversely a short tithi between two sunrises gets no day at all (kshaya). The lunar month still always contains exactly 30 tithis.
Which tithi is today?
It depends on your city — the tithi at YOUR local sunrise is the day's tithi. Check the panchang page for your city on this site; we compute it for 6,390 Indian cities and 3,800+ cities worldwide.