Lunar calendar

Calendar based only on the Moon

A lunar calendar is a calendar whose months record the cycles of the Moon's phases (synodic months, lunations). This in contrast to solar calendars, whose annual cycles are based on the solar year (which is about 11 to 12 days longer than twelve lunar months). It is also to be contrasted with lunisolar calendars, which also count lunar months but recover the accumulated differences by adding ("intercalating") a thirteenth leap month every few years.

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