Death Anniversary Tithi Calculator

Find the Hindu tithi and lunar month of a death, then the date that tithi falls on in any year at the place where the anniversary is observed.

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Calculator Functions

In the Hindu calendar a death anniversary is kept on the tithi (lunar day) of the death, in the same lunar month, so its date on the Gregorian calendar changes every year. The calculator finds that tithi and month, then the date they fall on in the year you choose.

The answer is the date at the place of the observance, which can be a day apart between India and other time zones. For the same calendar date each year, use the Anniversary Calculator. To count down to the date, use the Days To Go Calculator.

Death Anniversary Tithi Formula

A tithi is the time the Moon takes to gain 12° on the Sun. The first tithi starts at new moon, the 15th (Purnima) ends at full moon and the 30th (Amavasya) ends at the next new moon [1]. A tithi lasts 23 hours 37.5 minutes on average, but it can be as short as 19 hours 59 minutes or as long as 26 hours 47 minutes [1], and it can begin at any time of day. At 9:15 PM on August 23, 2019 in New Delhi the Moon was 270.39° ahead of the Sun. Since 270.39 ÷ 12 = 22.5, the tithi was number 23, the eighth of the waning half: Krishna Ashtami.

The lunar month and its name

In rites for the ancestors the month is lunar [2]. A month that ends at the new moon (amanta) runs from one new moon to the next and takes the name of the solar month in which its first new moon falls [1]. Solar months are counted along the sidereal zodiac, which Indian calendars measure from a fixed point on the ecliptic. In 2000 that point lay 23°51′25.5″ from the equinox [7].

When two new moons fall in one solar month, the month that starts at the first is the intercalary month (adhika or mala masa) and the month that starts at the second is the regular one (shuddha or nija) [1]. In calendars whose months end at the full moon (purnimanta), which the Hindi calendar uses, the waxing half keeps the same month name and the waning half carries the name of the following month [1]. So Shravana Krishna Ashtami in a new-moon-ending calendar is the same day as Bhadrapada Krishna Ashtami in a full-moon-ending one.

Which day the anniversary falls on

The yearly shraddha (pratyabdika or pratisamvatsarika shraddha) is performed every year on the day of the death, and in these rites the day means the tithi [2]. A tithi usually touches two calendar dates, so a rule has to pick one.

The afternoon rule is the calculator’s default. Aparahna, the afternoon, is the time laid down for shraddha, and one reading takes it as the fourth of five equal parts of the day [2]. Rites for the ancestors follow the tithi in force in the afternoon and at sunset [3]. The calculator splits the time from sunrise to sunset into five parts and picks the date on which the tithi is in force during the fourth. If that happens on two dates it takes the longer cover, and if on neither it takes the date on which the tithi is in force at sunset.

The sunrise rule matches printed calendars, which in most of India number each day by the tithi in force at sunrise [1]. In 2026 Ashvina Amavasya runs from 11:28 AM on November 8 to 12:32 PM on November 9 in New Delhi. It covers the whole afternoon period of November 8 (1:10 PM to 3:21 PM) and has ended before that of November 9, so the afternoon rule gives November 8. Sunrise on November 9 (6:39 AM) falls inside it, so the sunrise rule gives November 9. The result always lists both.

Intercalary months and missing details

When the death was in an ordinary month, the yearly shraddha is kept in the regular month of that name and not in an intercalary one [2]. For a death in an intercalary month, it is kept in the intercalary month in a year that has one, and otherwise in the ordinary month of the same name [2]. The calculator follows both rules and says so in the result. If only the month is known, the texts give the Amavasya of that month, and if only the tithi is known, that tithi in Margashirsha or Magha [2]. Either can be entered in the known-tithi function.

Sun, Moon and sunrise

The Moon’s longitude comes from the ELP 2000-82B lunar theory: the mean longitude, the 61 largest terms of the main series, the largest planetary term and the Earth-figure term [4]. The Sun’s longitude comes from Kepler’s equation with the orbital elements of the Earth-Moon barycentre [5], taken 499 seconds earlier for each astronomical unit of distance, the time its light takes to arrive [6]. Clock time is converted to the uniform time scale of those theories with ΔT [9].

H is the Sun’s hour angle at sunrise or sunset, φ the latitude and δ the Sun’s declination. The 90.833° allows for atmospheric refraction and the size of the Sun’s disk [8]. Sunrise in minutes of UTC is 720 − 4 × (longitude + H) − the equation of time, and sunset uses −H [8].

Limits of This Estimate

• Against NASA’s published times of new, quarter and full moons from 1901 to 2100 [10], these Sun and Moon positions are within a minute and a half. A tithi change that close to sunrise, to the afternoon period or to the time of death can move the answer by a day, and the result flags it. These estimates are based on the best available data and estimations.
• Panchangs differ. Almanacs worked from the Surya Siddhanta give other lengths for the months than modern positions do [1], and the texts hold more than one reading of the afternoon period [2]. Where your family’s or priest’s practice differs from the date shown, follow it.
• In rare years a lunar month is dropped (kshaya) [1] and calendars differ on the month names around it. The result flags those years.
• Sunrise is worked out for the city chosen, or for the latitude and longitude entered, up to 60° north or south. Dates run from 1900 to 2100.

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