One key difference between the Gregorian and the Ethiopian calendar is the number of months. While the Gregorian calendar has 12 months, the Ethiopian calendar has 13: 12 months, each with 30 days, and one intercalary month that has five days or six days on a leap year.
The Ethiopian calendar is seven to eight years behind the Gregorian calendar, due to the fact that the Ethiopian Orthodox Church disagrees with the Roman Catholic Church about when Jesus was born. The Ethiopian Orthodox Church believes Jesus' birth year to be 7 B.C., which it believes to be exactly 5,500 years after the world was created. As the Ethiopians count hours from dawn, the Ethiopian calendar also differs from the Gregorian calendar in terms of calculation of time.
The Ethiopian calendar is more closely related to the Egyptian calendar, following the same format for the number of months in a year and the days therein. The Egyptian calendar, like the Ethiopian calendar, is seven to eight years behind the Gregorian calendar. However, the Egyptian and the Ethiopian calendar differ with regard to the saints' days.
Some public holidays on the Ethiopian calendar that differ from those on the Gregorian calendar are the Ethiopian Christmas and Easter. Per the Gregorian calendar, they fall on Jan. 7 and April 27, respectively.