In short
A tithi is a lunar day: the time the Moon takes to move 12° further ahead of the Sun, so a full Moon cycle has 30 tithis, 15 in Shukla paksha (waxing) and 15 in Krishna paksha (waning). The vaar, the Hindu weekday, begins at local sunrise and not at midnight, so in the panchang a birth or event at 3 am still belongs to the previous day's vaar.
What a tithi measures
Seen from the Earth, the Moon moves faster than the Sun. The angle between them is called the elongation. Each time it grows by another 12°, one tithi ends and the next begins.
- At 0°, the Moon and Sun are together. That is the end of Amavasya (new Moon) and the start of Shukla Pratipada.
- At 180°, they are opposite. That is the end of Purnima (full Moon) and the start of Krishna Pratipada.
- 360° ÷ 12° = 30 tithis in one lunar month.
Because a tithi is based on the real positions of the Moon and the Sun, it starts at the same instant everywhere on Earth. Only the local clock time you read it at changes.
The two pakshas and the 15 tithi names
Each paksha has 15 tithis. The names repeat; only the last one differs.
| No. | Tithi | Shukla paksha ends at | Krishna paksha ends at |
|---|---|---|---|
| 1 | Pratipada | 12° | 192° |
| 2 | Dwitiya | 24° | 204° |
| 3 | Tritiya | 36° | 216° |
| 4 | Chaturthi | 48° | 228° |
| 5 | Panchami | 60° | 240° |
| 6 | Shashthi | 72° | 252° |
| 7 | Saptami | 84° | 264° |
| 8 | Ashtami | 96° | 276° |
| 9 | Navami | 108° | 288° |
| 10 | Dashami | 120° | 300° |
| 11 | Ekadashi | 132° | 312° |
| 12 | Dwadashi | 144° | 324° |
| 13 | Trayodashi | 156° | 336° |
| 14 | Chaturdashi | 168° | 348° |
| 15 | Purnima (Shukla) or Amavasya (Krishna) | 180° | 360° |
Festivals are tied to tithis. Chhath Sandhya Arghya, for example, falls on Kartik Shukla Shashthi. Diwali Lakshmi Puja falls on the Amavasya that the purnimanta calendar of north India calls Kartik Amavasya; the amanta calendar, used in western and southern India, calls the same night Ashvin Amavasya.
Why a tithi can be skipped or repeated
A tithi is not a fixed length. The Moon speeds up and slows down along its orbit, so the 12° gap sometimes closes quickly and sometimes slowly. A tithi can be noticeably shorter or longer than a solar day.
The civil calendar names each day by the tithi running at sunrise. That creates two special cases:
- Kshaya tithi (skipped): a short tithi begins after one sunrise and ends before the next. It never touches a sunrise, so no calendar day carries its name.
- Adhika or vriddhi tithi (repeated): a long tithi covers two sunrises, so two calendar days in a row carry the same tithi.
So if you search "aaj ki tithi" and find a tithi missing this month, or the same tithi twice, nothing has gone wrong; that is how the rule works.
Why vaar starts at sunrise
In the panchang, a day runs from one local sunrise to the next. The vaar (Ravivaar, Somvaar, Mangalvaar and so on) changes at sunrise, not at midnight as on a wall calendar.
So a child born at 3 am on what the clock calls Monday is counted under Ravivaar (Sunday) in the panchang, because Monday's sunrise has not come yet. Since sunrise depends on the city, the switch-over is local too.
The sunrise day and the tithi rules are traditional conventions of the Hindu calendar. They describe how the calendar is kept; they are not a claim that one day is better than another.
How SachAstro calculates this
We use our own engine, built on NASA JPL DE440 planetary data through Skyfield. The tithi is the Moon−Sun elongation divided by 12°. Sunrise and sunset use the Sun's upper limb with standard refraction, for the exact place; moonrise and moonset use the centre of the Moon's disc, topocentric. The vaar in every chart is counted from local sunrise. The zodiac is sidereal with the Lahiri ayanamsa. Times are rounded to the nearest minute, in IST. On 29 October 2026 we checked our results against a leading public panchang for 10 cities, and all were within 2 minutes.
Frequently asked questions
What is a tithi in simple words?
A tithi is a lunar day, the time it takes the Moon to get 12° further ahead of the Sun. There are 30 tithis in a lunar month.
What is the difference between Shukla paksha and Krishna paksha?
Shukla paksha is the waxing half, from Amavasya to Purnima, when the Moon grows brighter. Krishna paksha is the waning half, from Purnima to Amavasya.
Why is a tithi missing from the calendar this month?
That is a kshaya tithi: it started after one sunrise and ended before the next, so no day was named after it. The opposite case, where a tithi covers two sunrises, gives an adhika tithi.
If I was born at 3 am, which vaar is my birth?
In the panchang, your birth counts under the previous day's vaar, because the Hindu day starts at local sunrise. Born at 3 am on a Monday by the clock means Ravivaar in the panchang.
Does SachAstro count the vaar from sunrise?
Yes. Every chart we make counts the vaar from local sunrise at the place of birth, as the panchang does. You can make your kundli's first look free at app.sachastro.com/janm.