Moon Phase
🌕 Moon Phase on Your Birthday
See what shape the Moon was on the day you were born — New, Full, Crescent and more — from a pure astronomy calculation based on the synodic month.
1943-9-21
Last Quarter
~55% illuminated · Moon age ~21.7 days · waning
The 8 phases of the Moon
What is a Moon phase?
The Moon shines by reflecting sunlight, and the shape we see changes with the geometry of the Earth, Moon and Sun. One cycle from new moon to new moon takes about 29.5 days (the synodic month), passing through crescent, quarter, full and back. The illuminated fraction is how much of the Moon’s face looks lit.
※ This is an astronomy calculation from the synodic month (29.53 days) and days elapsed since a reference new moon. It simplifies the Moon’s orbital variations, so values are approximate (up to about ±1 day). The names are traditional; this is observational fact, not astrology. About our data