A tithi is a lunar day. It is the time the Moon takes to move exactly 12° ahead of the Sun. A full circle of 360° makes 30 tithis, which is one lunar month of about 29.5 days. The tithi at sunrise gives its name to the civil day.
Shukla and Krishna paksha
The month has two halves of 15 tithis each. In Shukla paksha (the bright half) the Moon grows from Amavasya (new moon) to Purnima (full moon). In Krishna paksha (the dark half) it fades from Purnima to Amavasya.
| No. | Tithi | Group |
|---|---|---|
| 1 | Pratipada | Nanda |
| 2 | Dwitiya | Bhadra |
| 3 | Tritiya | Jaya |
| 4 | Chaturthi | Rikta |
| 5 | Panchami | Purna |
| 6 | Shashthi | Nanda |
| 7 | Saptami | Bhadra |
| 8 | Ashtami | Jaya |
| 9 | Navami | Rikta |
| 10 | Dashami | Purna |
| 11 | Ekadashi | Nanda |
| 12 | Dwadashi | Bhadra |
| 13 | Trayodashi | Jaya |
| 14 | Chaturdashi | Rikta |
| 15 | Purnima / Amavasya | Purna |
The groups run in the order Nanda, Bhadra, Jaya, Rikta, Purna. Nanda tithis are for joy and celebration. Bhadra for health and routine work. Jaya for contests and victory. Rikta (Chaturthi, Navami, Chaturdashi) are usually avoided for new beginnings. Purna (Panchami, Dashami, Purnima) are good for finishing and starting alike.
Why a tithi is not 24 hours long
The Moon's speed against the Sun changes through the month, so a tithi can last from about 19 hours to about 26 hours. The average is 23 hours 37 minutes. A tithi often starts and ends in the middle of a civil day, which is why the panchang lists "tithi begins" and "tithi ends" times.
Tithi vriddhi and kshaya
- Vriddhi (extra tithi): when a tithi is long enough to touch two sunrises, it appears on two dates.
- Kshaya (lost tithi): when a tithi starts after one sunrise and ends before the next, it is not present at any sunrise, so it seems to be skipped.
This is why a festival date can look confusing. The rule for each festival (sunrise, midday, evening or midnight) decides which day is kept. Read more on our festival pages.
Which tithis are special
- Ekadashi (11th): fast for Vishnu. See the Ekadashi guide.
- Trayodashi (13th): Pradosh vrat for Shiva.
- Chaturthi (4th): Ganesha. Krishna Chaturthi is Sankashti, Shukla is Vinayaka.
- Purnima and Amavasya: full and new moon, days of charity, holy dips and ancestor rites.
Questions people ask
How is a tithi calculated?
The Moon's longitude minus the Sun's longitude is divided into 12° slices. Each time the difference crosses a multiple of 12°, a new tithi begins.
Why do two dates show the same tithi?
When a tithi is long (vriddhi), it is present at two sunrises, so it can show on two consecutive dates.
How long is a tithi?
Between about 19 and 26 hours, with an average of 23 hours 37 minutes.
What is the difference between Purnima and Amavasya?
Purnima is the 15th tithi of Shukla paksha (full moon). Amavasya is the 15th tithi of Krishna paksha (new moon).