Under this moon
What was the Moon phase on your birthday?
Enter any date from 1900 to this year — a birthday, an anniversary, a day that mattered — and see the Moon as it was: its phase, how much of it was lit, how far away it was, and what we know happened on that date.
How the answer is worked out
Calculated, not looked up
Your browser works out the Moon’s position from published astronomical algorithms (Meeus, Astronomical Algorithms). Checked against JPL Horizons and the US Naval Observatory for dates across 1900 to 2026, the lit fraction agrees to within 0.02 percentage points and the distance to within 50 km; the times of new and full moons agree to within about three minutes, so they are shown as “about”, to the nearest five.
One moment, named
The Moon changes through a day, so a date needs an hour attached. Unless you add one, the answer is for 12:00 UTC on that date, which is still the same date almost everywhere on Earth. A rounded 100% does not by itself mean the exact full moon fell on your date; the page shows when it did.
An illustration, not a photograph
The picture is this site’s rendering of that phase from Lunar Reconnaissance Orbiter data, drawn north up as the Moon looks from the Northern Hemisphere. It does not show the weather, the Moon’s colour or whether it was above your horizon that day.
History, kept honest
Events come from this site’s own history pages, each dated and sourced. Anything on your exact date comes first; the same day in other years is labelled as such. Nothing is shown as having happened on your date because the Moon matched.
More: methodology · the eight phases · this month’s moons · everything that happened under a known moon