Moon Phase
🌕 Moon Phase on Your Birthday
What shape was the Moon the night you were born? Pick your date below — then read what the two numbers underneath it actually mean, and when that same Moon comes back to your birthday.
On August 14, 1971 the Moon was a
Last Quarter
44%
illuminated
22.7
days into the cycle
Waning
shrinking
🎂 What’s your birthday?
Pick your date to see your full birthday profile — zodiac, life path and more.
The eight phases, in order
One full cycle — new Moon back to new Moon — takes 29.53 days. It is split into eight named phases, so each one lasts about 3.7 days. A phase is a stretch, not a single value: that is why two dates can both be called a Last Quarter and still show different percentages. The ranges below are what each name actually covers.
- New Moon 0–4% lit — the dark Moon, the turning point of the cycle
- Waxing Crescent 4–31% lit, growing
- First Quarter 31–69% lit, growing — exactly half at its midpoint
- Waxing Gibbous 69–96% lit, growing
- Full Moon 96–100% lit — fully lit, the other turning point
- Waning Gibbous 69–96% lit, shrinking
- Last Quarter 31–69% lit, shrinking — half again, on the way down yours
- Waning Crescent 4–31% lit, shrinking
How to read the two numbers
Illuminated fraction is how much of the disc you can see lit, from 0% at new Moon to 100% at full. It is not a straight line: the Moon spends longer looking nearly-full than you would expect, because the lit fraction follows a curve rather than climbing evenly.
Days into the cycle (Moon age) counts from the last new Moon — so 0 is new, about 14.8 is full, and it resets at 29.53. Two dates can share a phase name and still have different ages, which is why both numbers are shown.
Why your birthday Moon changes every year
A year holds about 12.37 lunar cycles — not a whole number. The leftover fraction means the Moon on your birthday shifts roughly 11 days along the cycle each year, so the phase you were born under is not the one you get on most birthdays.
After August 14, 1971, August 14 falls on a Last Quarter again in:
Same phase name, not an identical Moon — the illuminated fraction differs a little each time.
About this calculation
The phase is worked out from the synodic month (29.53058867 days) counted from a known new Moon, evaluated at midday for the calendar date you enter. This simple method ignores the small eccentricity of the Moon’s orbit, so a date sitting right on a boundary can be off by up to about a day — the percentage and the age are the precise part, the name is the label.
This is astronomy, not astrology: no personality or fortune is attached to a phase here. About our data