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How long is a synodic month?
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First complete printed title page for the Kalendarium (“Calendar”) by Regiomontanus, 1476.
A synodic month, also known as a lunation, is the time required for the Moon to complete one full cycle of its phases as observed from Earth, such as the interval between successive new moons or full moons.12
On average, a synodic month is 29.530588 mean solar days in length, which equates to 29 days, 12 hours, 44 minutes, and 3 seconds. Because of perturbations in the Moon's orbit, the actual duration of individual synodic months can vary slightly. This period is distinct from other lunar measurements, such as the sidereal month, which measures the Moon's return to the same position relative to the stars.2