Moon phase finder for birthdays and anniversaries
What did the moon look like on your birthday?
Enter your birth date to see the shape of the moon in the sky that day and its age in days. Works for anniversaries and any other date too.
The date is calculated on this device only. It is never sent or stored anywhere.
- Moon age (days since new moon)
- Lit portion of the moon
- Full moon before
- Full moon after
Your birth month's full moon
Traditional full-moon names from North American and other folk calendars — a custom, not an astronomical category.
Years your birthday falls on a full moon
Years the birthday moon matches the day you were born
The moon's phases and the calendar line up again about every 19 years (the Metonic cycle), so your 19th, 38th, 57th… birthdays tend to bring back the moon you were born under — though the match can drift off in some years and land on others. Shown: the first five years within a day of your birth moon age.
Calculated for noon on that date in your device's time zone.
What else is linked to the full moon?
What is moon age?
Moon age is the number of days since the last new moon. It starts at 0 at the new moon, reaches the first quarter after about 7 days, the full moon after about 15, the last quarter after about 22, and returns to the next new moon after about 29.5 days. Because the moon's shape follows its age, knowing the moon age on your birthday tells you what the moon looked like that night.
The eight phases
- New moon: age about 0. The moon sits near the sun and can't be seen
- Waxing crescent: a thin sliver in the evening sky
- First quarter: age about 7, the right half lit (as seen from the Northern Hemisphere)
- Waxing gibbous: more than half lit, growing toward full
- Full moon: age about 14 to 15
- Waning gibbous: rising later each night after the full moon
- Last quarter: age about 22, the left half lit
- Waning crescent: a thin sliver in the dawn sky
In the Southern Hemisphere the lit side appears mirrored.
Does being born on a full moon change anything?
"More babies arrive on full-moon nights" is a story told in maternity wards for generations. We counted 5,209 days of US birth records by moon phase to check — see Full moon and births for the answer.
How it's calculated
The instants of every new and full moon are computed with the astronomical algorithms in Jean Meeus, Astronomical Algorithms — the same calculation behind every verdict on this site — and the moon age is the time from the last new moon to noon on your date. Dates from 1900 to 2100 are supported.