Question 1

How is the moon phase calculated?

Accepted Answer

The moon phase is calculated using a known new moon reference date and the synodic month period (~29.53 days). The fractional part of the cycle determines the phase.

Question 2

What do the moon phases mean?

Accepted Answer

The main phases are: New Moon (0%), Waxing Crescent, First Quarter (50%), Waxing Gibbous, Full Moon (100%), Waning Gibbous, Last Quarter (50%), Waning Crescent.

Question 3

How accurate is this moon phase calculator?

Accepted Answer

It uses the mean synodic month which is accurate to within a few hours. For astronomical precision, consider dedicated ephemeris software.