Vedic BirthdaysWhat is a Vedic birthday?
A Vedic birthday is the day each year when the moment of your birth comes round again on the traditional Hindu calendar — not on the Gregorian one.
Tithi, not date
The Hindu calendar is built on the Moon. A tithi is a lunar day: one thirtieth of the cycle from one new moon to the next, or the time the Moon takes to gain 12° on the Sun. There are thirty in a lunar month, fifteen in the bright half (Shukla paksha) and fifteen in the dark half (Krishna paksha). Your janma tithi is the tithi that was running when you were born. Your Vedic birthday is the day that same tithi returns in the same lunar month.
In the Tamil tradition the reckoning uses the nakshatra instead: the star, one of twenty-seven divisions of the Moon's path, that the Moon was in at your birth. The birthday is the day that star comes round again.
How it differs from your Gregorian birthday and a solar return
Your Gregorian birthday is the same calendar date every year because the Gregorian calendar follows the Sun. A lunar year of twelve lunar months is about eleven days shorter than a solar year, so a tithi lands on a different Gregorian date each year. Over a few years it drifts earlier, and then an extra month is added and it jumps later again.
A solar return, as used in Western astrology, is the moment the Sun returns to its exact birth position. That is a different idea: it is tied to the Sun's position, not to a tithi or nakshatra, and this site does not calculate it.
Why festivals move too
Hindu festivals follow the same rule as a Vedic birthday. Rama Navami is the ninth tithi of the bright half of Chaitra, and Krishna Janmashtami is the eighth tithi of the dark half in the month of Shravana or Bhadrapada, depending on the regional month system. They shift on the Gregorian calendar every year for exactly the reason a Vedic birthday does. If your family already looks up the date of Diwali each year, you already understand how a Vedic birthday works.
What we calculate
You give us your date, time and place of birth, and the tradition your family follows. We find the tithi or nakshatra that was running at that moment, in your lunar month, and return the next Gregorian date on which it comes back. The place matters because it converts your local birth time to a universal time and fixes the local sunrise used to decide the civil day. Adhika (leap) months are handled so that a birthday is not placed in an extra month.
We do not draw a birth chart, read a dasha or make predictions. The result is a calendar date and the details behind it: tithi or nakshatra, lunar month and year.