Panchang guide / Tithi
What is a tithi? The 30 lunar days explained
A tithi (तिथि) is a lunar day. It is measured not by the clock but by the Moon’s distance from the Sun: every time the Moon pulls another 12° ahead of the Sun, a new tithi begins.
How a tithi is calculated
Take the Moon’s longitude, subtract the Sun’s, and divide by 12°. At new moon the two are together (0°), and the first tithi begins. At 180° the Moon is opposite the Sun: full moon. At 360° they meet again and the month ends. 360° ÷ 12° = 30 tithis.
The Moon’s speed changes through its orbit, so tithis are not equal in length. A tithi can last from about 20 hours to about 27 hours. That is why tithis rarely start at sunrise or midnight.
Shukla and Krishna paksha
The month has two halves, or pakshas. In Shukla paksha, the bright half, the Moon waxes from new to full; it ends with Purnima. In Krishna paksha, the dark half, the Moon wanes; it ends with Amavasya. The first fourteen tithis carry the same names in both halves.
| # | 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 (bright half) · Amavasya (dark half) | Purna |
The groups repeat every five tithis and are used in muhurat: Nanda (joyful), Bhadra (auspicious), Jaya (victorious), Rikta (empty, generally avoided for beginnings) and Purna (full).
The sunrise rule
A calendar date needs one tithi, but a tithi can start at any hour. The rule is simple: the tithi running at local sunrise is the tithi of that day (udaya tithi). It stays the day’s tithi even if it ends an hour after sunrise.
Two odd cases follow from this:
- A skipped tithi (kshaya): a short tithi that starts after one sunrise and ends before the next never touches a sunrise, so no date carries its name.
- A doubled tithi (vriddhi): a long tithi that spans two sunrises gives its name to two dates in a row.
Festivals often follow their own rule instead of sunrise. Diwali’s Lakshmi Puja needs Amavasya in the evening, Janmashtami needs Ashtami at midnight, and Ekadashi has rules of its own (see Ekadashi).
Why your city matters
The moment a tithi ends is the same worldwide, but sunrise is not. So the same tithi can fall on different dates in Delhi, London and Toronto. Always use a panchang calculated for where you are.
Today’s tithi: see it for your city, with the exact time it ends.
Sources: tithi groups and their use as in the classical muhurta texts, such as Muhurta Chintamani. Calculations on LotusAstro use the Swiss Ephemeris.