The Moon cycle, also known as the lunar cycle or synodic month, lasts about 29.5 days on average. This is the time it takes for the Moon to complete one full cycle of phases, from new Moon to new Moon, which is approximately 29.53 days (29 days, 12 hours, 44 minutes, and 3 seconds)
. There is a distinction between two key periods related to the Moon's orbit:
- The sidereal month is about 27.3 days and represents the time it takes the Moon to orbit Earth once relative to distant stars.
- The synodic month (the lunar cycle of phases) is longer, about 29.5 days, because as the Moon orbits Earth, Earth itself moves around the Sun, so the Moon must travel a bit further to reach the same phase position relative to the Sun and Earth
Thus, the lunar cycle that we observe in the changing phases of the Moon repeats roughly every 29.5 days.
