Lunar day

For the tidal lunar day of about 24 hours and 50 minutes, see Tide. "Moon day" redirects here. For the day of the week named after the Moon, see Monday.

A lunar day is the time it takes for Earth's Moon to complete on its axis one synodic rotation, meaning with respect to the Sun. The synodic period is about 29.53 Earth days, which is about 2.2 days longer than its sidereal period.

Informally, a lunar day and a lunar night are each approximately 14 Earth days. The formal lunar day is therefore the time of a full lunar day-night cycle.

Due to tidal locking, this equals the time that the Moon takes to complete one synodic orbit around Earth, a synodic lunar month. Because of this synchronicity the cycle of lunar phases observed from Earth are the lunar day on the near side of the Moon.

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