Lunar month vs calendar month
Compare Moon cycles with Gregorian calendar months.
The synodic month
A synodic month, measured from one similar lunar phase to the next, averages about 29.5 days. The exact interval varies slightly.
Calendar months
Gregorian months are civil divisions of 28 to 31 days and are not synchronized to lunar phases.
Lunar and lunisolar calendars
Some calendars organize months by the Moon and add rules to stay aligned with seasons. Conversions require the specific calendar system and year.
Related month guides
- Where the month names come from — The Roman roots behind the twelve English month names.
- How many days are in each month? — A complete guide to 28-, 29-, 30- and 31-day months.
- How to add or subtract calendar months — Handle month-end dates without overflowing into the wrong month.