How long does it take for the moon to go through one set of phases?

Answer 1

29 days, 12 hours and 44 minutes. This is not the same as the time taken for the moon to make one orbit of the earth though.

Relative to the background stars and ignoring the earth position relative to our sun, the moon takes 27 days 7 hours and 43 minutes to orbit the earth - the sidereal orbit.

During this time, the earth has progressed around the sun a little, on its orbit around the sun. For the moon to get back to exactly the right phase, it takes a little longer, 29 days, 12 hours and 44 minutes in total from full moon to the next full moon. This is known as the synodic period. The moon will have made just over one orbit relative to the background stars, and will have moved round slightly to be in front of some different stars to those at the previous full moon.