🌙 Lunar Phase & Illumination

Phase, illumination fraction, age and a drawn disc for any date and time — plus the next new and full Moons and how much moonlight is washing out the sky. Runs entirely offline.

Pick a date to see the phase.
Method and accuracy

Uses the mean synodic month of 29.53058867 days from a known new-Moon epoch (2000-01-06 18:14 UTC). Phase age and illumination are good to roughly half a day and a few percent; the Moon's real orbit is eccentric and inclined, so exact new and full Moon times can differ by up to about 14 hours. Times are handled in UTC — convert to your local zone before planning an outing.