The Thirty Tithis: Meaning, Groups, Deities and How the Day Is Named

A tithi is the basic day of the Hindu lunar calendar. It is not the same as the civil day from midnight to midnight, or from sunrise to sunrise. It is measured by the Moon: a tithi is complete each time the Moon gains twelve degrees on the Sun, measured along the ecliptic, the Sun’s path in the sky. Since a full circle is 360 degrees, a lunar month holds thirty tithis, and every festival, vrat and muhurat in the Hindu calendar is tied to one of them.

This page explains how the tithis work and how they are grouped. The sixteen pages below it take the tithi names one at a time: what each is, the deity a common list gives it, the festivals and vrats that fall on it, and what muhurat practice says. To see which tithi is running right now in your own city, open the daily panchang.

How a tithi is measured

At the new Moon the Sun and Moon are in the same direction, and the angle between them, called the elongation, is zero. The Moon moves faster across the sky than the Sun, so the angle grows, by about twelve degrees a day on average. Tithi number one lasts while the elongation rises from zero to twelve degrees, tithi two from twelve to twenty-four, and so on, until at a hundred and eighty degrees the Moon is opposite the Sun and the Moon is full. The count then continues from a hundred and eighty to three hundred and sixty, and at the end the Moon is again with the Sun and the cycle starts afresh.

A tithi therefore starts and ends at an exact astronomical moment, which is the same instant everywhere on Earth. The clock time and the civil date of that moment depend on where you live, which is why a festival can fall on different dates in New Delhi and New York, and why the festival pages calculate the day for each city.

Shukla and Krishna paksha

The thirty tithis are split into two halves of fifteen, called pakshas, a word meaning wing or fortnight. In Shukla paksha, the bright half, the Moon grows from the new Moon to the full Moon. It begins at the end of Amavasya (new Moon day) with Pratipada and closes with Purnima, the full Moon day. In Krishna paksha, the dark half, the Moon wanes. It begins after Purnima with Pratipada again and closes with Amavasya.

So the same names repeat. There is a Shukla Panchami and a Krishna Panchami, fifteen days apart, and a calendar always has to say which one it means. Counted through the month, the tithis are numbered one to thirty, with the Krishna tithis numbered sixteen to thirty. The last of each half is named differently: the fifteenth tithi of the month is called Purnima and the thirtieth is called Amavasya, which is why sixteen names cover thirty tithis.

Which tithi names the day

A tithi does not begin at sunrise, so a civil day can contain parts of two tithis. The common rule is that the tithi in force at sunrise gives its name to the day, and a date in a panchang usually means the sunrise tithi. This is the rule used by the daily panchang, and most almanacs list the start and end times of each tithi next to it.

Observances often use a different test. Some are fixed by the tithi in force at midday, at midnight, at sunset or in the afternoon, according to when the rite is done. Janmashtami follows the tithi at midnight, Ram Navami the tithi at midday, Pradosh Vrat the tithi in the evening and the rites for ancestors the afternoon. When you read that a festival is on an unexpected day, the rule that applies to that rite is usually the reason.

Kshaya and vriddhi tithis

A tithi is not a fixed number of hours. The Moon does not travel at a steady speed: its orbit is an ellipse, so it moves faster in some weeks and slower in others, and the Sun’s apparent speed varies a little through the year as well. As a result a tithi can be as short as about nineteen hours or as long as about twenty-six. A civil day from one sunrise to the next is close to twenty-four hours, so the two do not line up.

When a tithi is short enough to begin after one sunrise and end before the next, no sunrise falls in it, and no civil day carries its name. This is a kshaya tithi, meaning a lost or diminished one, and the calendar jumps from the preceding tithi to the following one. When a tithi is long enough to be in force at two successive sunrises, two civil days carry its name. This is a vriddhi tithi, an increased or repeated one.

Both happen several times a year. Thirty tithis fit into about twenty-nine and a half days, so over a year more tithis are skipped than repeated, and the lunar year is shorter than the solar one by about eleven days. The extra month that the calendar adds from time to time, covered on the page on Adhika Masa, keeps the lunar year in step with the seasons.

The five groups

Muhurat texts sort the fifteen tithis of a paksha into five groups of three, and each group is traditionally linked to a kind of undertaking. The groups are Nanda, Bhadra, Jaya, Rikta and Purna, taken in turn through the first fifteen tithis. They are classifications used by almanacs, and they do not mean that every day in a group is lucky or unlucky.

In the dark half the same grouping is applied to the numbers one to fifteen of that half, and Amavasya is treated as the Purna tithi that closes it. Sources and regions differ on the finer points, so where a tithi page says that almanacs “generally” prefer or avoid a day, that is a common practice and not a universal rule.

The deities of the tithis

Tradition gives each tithi a presiding deity. The table below gives a common list. Lists differ between texts, and for several tithis another name appears elsewhere, so the pages say “a common list” and put your own family’s tradition first.

The sixteen tithi pages

The Ekadashi and Amavasya pages explain the tithi itself and leave the calculated dates to the festival pages for Ekadashi and Amavasya.

How tithis connect to months, festivals and muhurat

A lunar month is a run of thirty tithis, from one new Moon to the next in the amanta reckoning, or from one full Moon to the next in the purnimanta. The two systems, explained on the page about amanta and purnimanta, give the dark half the name of the earlier or the later month, which is why one festival may be listed under two month names. The months, years and seasons are in the Hindu calendar section.

For choosing a day for a ceremony, the tithi is one of five parts of the panchang, with the weekday, the nakshatra, the yoga and the karana. A good tithi alone does not make a good date. The birth charts of the people involved, the lagna of the moment and the position of the Moon in each chart are also checked by a family astrologer, which a general list cannot do. The muhurat section explains how the parts fit together, and the samskaras guide lists the life ceremonies for which families usually look for a day.

Frequently asked questions