It takes the Moon about 29.53 days (29 days, 12 hours, 44 minutes) to complete the cycle, from big and bright to small and dim and back to big and bright. The phase when the Moon passes between the Earth and Sun is called the "new Moon". The next phase of the Moon is called the "waxing crescent", followed by the "first quarter", "waxing gibbous", then a full Moon. A full Moon occurs when the Moon and Sun are on opposite sides of the Earth. As the Moon continues its orbit it becomes a "waning gibbous", "third quarter", "waning crescent", and finally back to a new Moon. People used the Moon to measure time. A month is approximately equal in time to a lunar cycle.