The Moon's phase is fixed by its elongation from the Sun, and Vedic astrology reads that same elongation as the tithi: every 12 degrees the Moon gains on the Sun completes one of the 30 tithis of the lunar month. Enter any date, including your date of birth, to see the phase, the tithi running at local sunrise, the paksha it belongs to and the time it ends.
A phase is not a property of the Moon on its own; it is the angle between the Moon and the Sun as seen from the Earth. That angle grows from zero at the new moon to 180 degrees at the full moon and back to zero, which is why the same cycle can be described either as a shape in the sky or as a number of degrees.
As the Moon orbits the Earth, the angle between the Moon and the Sun changes, so the sunlit portion we see grows and shrinks over a cycle of about 29.5 days. This cycle is commonly marked by four main phases:
Vedic astrology measures this same cycle as tithi and paksha rather than as a percentage of illumination. A tithi is the time the Moon takes to gain 12° on the Sun, so the lunar month holds 30 tithis: 15 in the waxing Shukla Paksha (Pratipada to Purnima) and 15 in the waning Krishna Paksha (Pratipada to Amavasya).
The tithi at the moment of your birth is your Janma tithi. It is used to celebrate the traditional tithi-based birthday and appears in muhurta and festival timing. This calculator reports the phase, tithi and paksha for any date you choose, and for your date of birth.
For a birth Moon phase, enter your date of birth. Note what the page can and cannot know: the tithi is evaluated at sunrise in the city the page is set to, not at the hour and place you were born. That is close enough for a tithi-based birthday on most dates, but where a tithi changes near your birth hour, cast the full kundli instead, which is computed for your birth moment and birth place.
The tithi comes straight from the elongation: subtract the Sun's longitude from the Moon's, take the result modulo 360, divide by 12 degrees and add one. Tithis 1 to 15 are the waxing Shukla Paksha and 16 to 30 the waning Krishna Paksha, with 15 Purnima and 30 Amavasya. Positions are sidereal on the Lahiri ayanamsha and computed to sub-arcsecond precision, though the elongation is a difference of two longitudes, so the ayanamsha cancels out of the tithi itself.
The tithi shown is the one running at local sunrise on the date you choose, because a Hindu day runs from sunrise to the next sunrise rather than from midnight. The end time printed beside it is when that tithi actually gives way to the next. The illumination percentage is derived from the same elongation, so it moves in twelve degree steps along with the tithi and is a geometric figure rather than a photometric measurement.
A Moon phase (new, waxing, full, waning) describes how much of the Moon is lit, while a tithi is the precise Vedic lunar day - one of 30, each defined by another 12° the Moon gains on the Sun. The paksha tells you whether that tithi falls in the waxing Shukla half or the waning Krishna half of the month.
It is the phase, tithi and paksha of the Moon on the day you were born. Enter your date of birth and the tool shows your Janma tithi, which is used for tithi-based birthdays and in traditional timing.
Amavasya is the new-moon tithi that closes each Krishna Paksha, and Purnima is the full-moon tithi that closes each Shukla Paksha. Their exact dates shift every month, so enter a date to see which tithi applies.
Subtract the Sun's longitude from the Moon's, take the result modulo 360, divide by 12 degrees and add one. Each tithi is therefore 12 degrees of elongation rather than a fixed number of hours, so tithis are not all the same length: one can run several hours longer or shorter than another as the two bodies speed up and slow down.
The Hindu day, which runs from sunrise to the next sunrise. The tool reports the tithi running at local sunrise on the date you choose and prints the time it ends. A tithi that begins in the afternoon is therefore listed against the following date, which is the usual reason an almanac and a civil calendar appear to disagree by a day.
For educational purposes. Astrological interpretations are traditional and not a substitute for professional advice.