structural:reformatting, information:classification
Coptic and Ethiopian calendars

The Coptic calendar has 13 months, 12 of 30 days each, and one at the end of the year of 5 days, or 6 days in leap years. The Coptic Leap Year follows the same rules as the Julian Calendar so that the extra month always has 6 days in the year before a Julian Leap Year. The Ethiopian calendar has 12 months of 30 days plus 5 or 6 epagomenal days, which comprise a 13th month.