Why Ethiopia has 13 months in a year?

On the other hand, Ethiopia has accepted the Coptic Calendar, which is quite different from the Gregorian calendar. The Coptic Calendar has 13 months of which 12 months comprise of 30 days each, and a 13th month at the end of the year called the intercalary month usually has 5 days and 6 days in a leap year. read more

Like the Coptic calendar, the Ethiopic calendar has 12 months of 30 days plus 5 or 6 epagomenal days, which comprise a thirteenth month. The Ethiopian months begin on the same days as those of the Coptic calendar, but their names are in Ge'ez. read more