Ethiopians have a different naming system to the family name-based Western system. Children add the given names of their father and paternal grandfather consecutively to their own given name. For compatibility purposes, as is done in passports, the grandfather’s given name is taken as a family surname, and a person’s given name and his/her father’s given name form the first name.

Ethiopian calendar and Oromo calendar

Model commemorating the Obelisk of Aksum’s return to Ethiopia, which shows the date of its departure and return according to the Ethiopian calendar

Ethiopia has several local calendars. The most widely known is the Ethiopian calendar, also known as the Ge’ez calendar. It is based on the older Alexandrian or Coptic calendar, which in turn derives from the Egyptian calendar. Like the Coptic calendar, the Ethiopian calendar has twelve months of exactly 30 days each plus five or six 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.

Like the Julian calendar, the sixth epagomenal day—which in essence is a leap day—is added every four years without exception on 29 August of the Julian calendar, six months before the Julian leap day. Thus, the first day of the Ethiopian year, 1 Mäskäräm, for years between 1901 and 2099 (inclusive), is usually 11 September (Gregorian), but falls on 12 September in years before the Gregorian leap year.

Another prominent calendrical system was developed around 300 BC by the Oromo. A lunar-stellar calendar, this Oromo calendar relies on astronomical observations of the moon in conjunction with seven particular stars or constellations. Oromo months (stars/lunar phases) are Bittottessa (Iangulum), Camsa (Pleiades), Bufa (Aldebarran), Waxabajjii (Belletrix), Obora Gudda (Central Orion-Saiph), Obora Dikka (Sirius), Birra (full moon), Cikawa (gibbous moon), Sadasaa (quarter moon), Abrasa (large crescent), Ammaji (medium crescent), and Gurrandala (small crescent).