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In short
Purnima is the full-Moon day, the fifteenth tithi and the last of the bright half, when the Moon stands opposite the Sun. This app reaches it as tithi 15 with the phase label Full Moon; no rule in the engine singles Purnima out by name.
What the term means
Purnima is the full Moon: the fifteenth tithi, which closes the Shukla Paksha. The Moon has moved to the far side of the sky from the Sun and is fully lit, rising around sunset. The tithi after it opens the Krishna Paksha.
Where the term comes from
Jyotisha Siddhanta Sara (Ch. II) ends the bright half on the full-moon day, when Sun and Moon face each other. BPHS Ch. 27 Sl. 10-11 build Paksha Bala from the Moon's distance from the Sun, which favours benefics most near this opposition. The classical texts in the corpus speak of a "full Moon" in yogas rather than of Purnima by name: the Bhrigu Sutras commentary calls the full Moon "a first class benefic", and Daivajna Vallabha reads a full Moon in the ascendant aspected by Jupiter as a sign of recovery in a query chart.
How this app uses it
The engine measures the Moon's sidereal distance ahead of the Sun and cuts it into thirty tithis of 12 degrees; tithi 15 is Purnima. The same distance gives the phase label (Full Moon near opposition) and the illumination percentage shown on the Moon phase calculator. In muhurat scoring Purnima counts as a Shukla tithi that is not on the avoid list; there is no separate full-Moon rule.
Because a tithi is defined by the angle between Moon and Sun, not by the calendar date, Purnima can begin at any hour. The panchang reports the tithi running at local sunrise, so the day it labels Purnima is the one whose sunrise falls inside the fifteenth tithi.
Pages that use this term
- Moon phase calculator - tithi, phase and illumination.
- Panchang calculator - the tithi at local sunrise.
- Muhurat calculator - how a full-Moon window scores.
- The Moon in Vedic astrology - the full Moon in the texts.
- Moon sign and nakshatra - phase beside sign.
Related terms
Moon Phase and Tithi
The tithi, the paksha and how much of the Moon was lit on your birth date.
This date is sent only to compute the answer. Nothing is stored, no account is created, and no email is asked for.