Lunar Calendar

moon · timekeeping · astronomy · culture

Months match Moon cycles. A lunar calendar divides the year into months that follow the Moon's phases. Each month lasts about 29 or 30 days, which is how long it takes the Moon to go from full to full again.

Different from sun calendars. Most calendars we use today, like the Gregorian calendar, track Earth's journey around the Sun. Lunar calendars instead watch the Moon go through its light and dark phases.

Islamic calendar is lunar. The Islamic calendar is the most common lunar calendar used today. It has 354 days in a year, which means Islamic holidays shift about 11 days earlier each year on the regular calendar.

Months stay in sync with Moon. Because lunar months follow the actual Moon's cycle, the calendar always lines up with what you see in the night sky. You'll never be surprised by when a full moon appears.

Some calendars add leap months. Lunisolar calendars, which use both Moon and Sun, occasionally add an extra thirteenth month to keep their seasons from drifting. This keeps winter from slowly moving toward summer over time.