Coptic

The Coptic calendar originated in agrarian Egypt and uses a cycle of 12 months of 30 days and one month consisting of either 5 or 6 days to add up to one full year as defined by the Julian calendar, the Coptic calendar was used up until 1875 in Egypt before being replaced by the Gregorian calendar. Like the Julian calendar, it uses an invariable 4 year cycle for leap years.