What is a lunar cycle?
A lunar cycle is the time from one new moon to the next, known as the synodic month.
29.53 days on average
The Moon needs 27.3 days to circle Earth once, but because Earth moves along its orbit around the Sun meanwhile, it takes just over two extra days for the same phase to return.
Why cycles differ in length
The Moon's orbit is elliptical and perturbed by the Sun, so a cycle can last anywhere from about 29.2 to 29.9 days. That is why this site calculates every event individually.
Frequently asked questions
How many full moons are there in a year?
Usually twelve, occasionally thirteen. A second full moon within one calendar month is called a blue moon.