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. (September 2017)
The Ethiopian calendar (Amharic: የኢትዮጵያ ዘመን አቆጣጠር; yä'Ityoṗṗya zämän aḳoṭaṭär) is the principal calendar used in Ethiopia and also serves as the liturgical year for Christians in Eritrea and Ethiopia belonging to the Eritrean Orthodox Tewahedo Church, Ethiopian Orthodox Tewahedo Church, Eastern Catholic Churches and Coptic Orthodox Church of Alexandria. It is a solar calendar which in turn derives from the Egyptian Calendar, but like the Julian Calendar, it adds a leap day every four years without exception, and begins the year on August 29 or August 30 in the Julian Calendar. A gap of 7–8 years between the Ethiopian and Gregorian Calendars results from an alternative calculation in determining the date of the Annunciation.
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. The 6th epagomenal day is added every 4 years, without exception, on August 29 of the Julian calendar, 6 months before the corresponding Julian leap day. Thus the first day of the Ethiopian year, 1 Mäskäräm, for years between 1900 and 2099 (inclusive), is usually September 11 (Gregorian). However, it falls on September 12 in years before the Gregorian leap year.