Editing Intercalation (timekeeping) (section)

== Lunisolar calendars ==
The solar year does not have a whole number of lunar months (it is about 365/29.5 = 12.37 [[Lunar_month#Synodic_month|lunation]]s), so a lunisolar calendar must have a variable number of months per year. Regular years have 12 months, but embolismic years insert a 13th "intercalary" or "leap" month or "embolismic" month every second or third year. Whether to insert an intercalary month in a given year may be determined using regular cycles such as the 19-year [[Metonic cycle]] ([[Hebrew calendar]] and in the [[Computus|determination of Easter]]) or using calculations of lunar phases ([[Hindu calendar|Hindu lunisolar]] and [[Chinese calendar]]s). The [[Buddhist calendar]] adds both an intercalary day and month on a usually regular cycle.