How many types of calendars are there?
List of calendars
Darian calendar (for Mars)
Discworld calendar (fictional)
Galactic Standard Calendar (from Star Wars, fictional)
Gethenian Calendar (fictional, notable for the current year always being designated as Year One)
Lunar Standard Time[6] (for the Moon)
Middle-earth calendars (fictional)
Stardates (from Star Trek, fictional)