Moon Phase Calculator

Mean cycle calculation. The Moon's synodic period is 29.5306 days on average (the time between two new moons). This calculator uses that average from a known reference new moon (2000-01-06 18:14 UT) to project any date. Real cycles vary by ±~6 hours due to orbital eccentricity, so the predicted dates may be off by a few hours. For exact astronomical events, check a service that uses the full ELP/MPC ephemeris.