If you travel to Ethiopia and pick up a newspaper, you might be shocked to discover that you’ve apparently gone back in time — by about eight years! Relax; that taxi cab you took wasn’t a DeLorean. You’re simply in a part of the world that doesn’t use the Gregorian calendar system. Ethiopia – as well as the Eritrean Orthodox Church in Eritrea – uses the Ge’ez calendar, which is based on the ancient Coptic calendar.
The Ethiopian calendar begins in September, and consists of 12 months of 30 days each, followed by a thirteenth month of just five days (or six days in a leap year). The 7-8 year variation between the Ethiopian and Gregorian calendars is due to a difference in calculation of the Annunciation of Jesus Christ.
Wikipedia: Ethiopian Calendar