Calendar makers eventually decided to stick with a solar year of 365 days (with a leap year every fourth year) and to make the months vary between 30, 31, and 28 days. The cycle of the phases, like from full moon to full moon, takes 29 and 1/2 days. Because of this, moon phases can happen anywhere during the months. 6: So exactly how long does it take the moon to orbit the Earth? Answer: This explanation can be a bit confusing, so have patience. The moon takes 27 1/3 days to orbit the earth once, but the number of days between one full moon and the next full moon is 29 1/2 days.