First Quarter at birth
First Quarter illustration
At first quarter, about half the Moon appears lit. The terminator runs roughly down the middle; people sometimes call this a half moon.
Quarter moons mark a neat geometric checkpoint halfway from new toward full.
Place in the cycle
The Moon takes a bit over twenty-nine and a half days to return to the same phase. The First Quarter is the third of the eight labels this site uses between one new moon and the next.
How this site estimates your phase
The birthday calculator has your date, not your birth minute. We evaluate a simple average lunar cycle at local noon and map that progress into eight named windows. That is good enough for curiosity and teaching; orbital ephemerides used by observatories are tighter when you need precision.
Read more in methodology or return to the moon phases hub.
Common questions
What does a First Quarter look like?
From Earth you see illumination that is about 50% and waxing. Exact appearance still depends on your latitude, the Moon's path, and weather.
How does the calculator decide I had a First Quarter?
It estimates phase at local noon on your birth date with a mean synodic-month model, then bins the result into one of eight classic names.
Can the label be wrong without a birth time?
Yes, near phase boundaries. Without clock time and location, neighboring names can be equally plausible.