Vedic BirthdaysJanma tithi
Your janma tithi is the lunar day you were born on. It is the basis of the Vedic birthday for most of India.
Thirty tithis, two halves
A lunar month has thirty tithis. The fifteen from new moon to full moon are Shukla(bright) paksha, ending with Purnima or Pournami. The fifteen from full moon to new moon are Krishna (dark) paksha, ending with Amavasya. Each is numbered Pratipada (first), Dwitiya, Tritiya and so on up to Chaturdashi, followed by Purnima or Amavasya. A tithi ends when the Moon has moved 12° further from the Sun than where the tithi began, so tithis are not all the same length: they run roughly nineteen to twenty-six hours.
Amanta and Purnimanta months
The tithi is the same everywhere; what differs is where the lunar month is said to begin.
- Amanta (Amavasya-ending) months run from one new moon to the next. This is followed in Andhra Pradesh, Telangana, Karnataka, Maharashtra, Gujarat and other regions. The dark half of a month is the end of that month.
- Purnimanta (Pournami-ending) months run from full moon to full moon. This is common in North India. The dark half is counted as the start of the next month, so the same day can carry a different month name than in an Amanta calendar.
That is why a Krishna paksha birthday can be in "Ashwina" for one family and "Kartika" for another while falling on the same civil day. Choose the system your family already uses for festivals.
Adhika masa
Twelve lunar months are shorter than a solar year, so about every three years a lunar month with no solar transition is added: the adhika masa, or leap month. It repeats the name of the month that follows it. Our calculation matches your tithi to the ordinary (nija) month, so an adhika month does not pull your birthday into the wrong place. Rarely a month is skipped (kshaya), which also shifts the date.
What the sunrise convention means here
Traditionally a tithi belongs to the civil day on which it is in force at sunrise. We compute the tithi that was running at your birth time, then find the next matching civil date, using local sunrise at your current place to decide which day the tithi is observed on. Some almanacs differ in edge cases, so a priest or a family almanac can differ from the result by a day when a tithi ends close to sunrise.
Find your janma tithi birthday
On the calculator, choose Amavasya-based (Amanta) if your family counts the month from the new moon, or Purnima-based (Purnimanta) if it counts from the full moon, then enter your birth date, time and place.