Moon phase calculator

Explore the lunar phase and approximate illuminated fraction for an entered instant.

Choose the time zone of the birthplace, not your current location. If the birth time is unknown, a sign or Nakshatra near a boundary may be uncertain.

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Your entries are used for this calculation only. They are not added to a profile or included in share links.

How this works

Phase uses the Sun–Moon longitude difference. Illumination uses (1 − cos(angle)) / 2, a simplified geocentric approximation; it is not local moonrise or an observance-time decision.

Approximate geocentric Sun/Moon calculations using the existing Meeus-based engine and a linear Lahiri ayanamsa. Near sign/Nakshatra boundaries, verify with a precise ephemeris. This is not a full Kundli.

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