Moon phases
Over roughly twenty-nine and a half days the Moon’s bright face grows from dark to full and back again. Birthday charts love those eight familiar names; astronomy explains them as geometry between Sun, Moon, and Earth.
Check your birth date in the calculator, or read how we estimate phase without a birth time.
How phases work
We always see sunlight bouncing off the Moon. As the Moon orbits Earth, that sunlight covers changing portions of the nearside. New moon hides the lit half from us; full moon shows it fully; quarters and crescents fill the steps between.
NASA and other educators publish the same eight classroom labels used here. Festivals and folklore add stories on top; the geometry underneath stays the same.
Common questions
What moon phase does the calculator show?
An approximate phase for your birth calendar date, estimated at local noon with a mean lunar-month model, then named as one of eight classic phases.
Why isn’t it exact?
Exact phase needs birth time and location. Date-only input keeps the answer honest about that uncertainty.
Are phase names the same as astrology?
The eight names describe sunlight on the Moon as seen from Earth. Separate moon-sign astrology uses different charts entirely.
