The many calendars make use of one ore more of the following astronomical cycles:
Year Cycles[]
- Tropical year: about 365.2422 days.
- Sidereal year: about 365.2564 days.
Month Cycles[]
- Synodic month: about 29.53059 days.
Other Cycles[]
- Metonic cycle: 19 years approximated to 235 synodic months, sometimes approximated to 6940 days.
- Callippic cycle: Four Metonic cycles approximated to 6940 days less one day (76 years).
- Hipparchic cycle Four Callippic cycles less one day (304 years).
- Full moon cycle Cycle of apparent size and age of full moon lasting just under 14 synodic months
- Sothic cycle A cycle of 1461 years of 365 days equivalent to 1460 Julian Calendar years.
