Ethiopia 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. Also, a seven- to eight-year gap between the Ethiopian and
Unit of time year cannot be divided into 12 28-day months since 12 times 28 is 336, well short of 365. The lunar month (as defined by the moon's rotation) is not 28 days but 28.3 days. The year, defined in the Gregorian calendar as 365.24 days has to be adjusted with leap days and leap seconds. Consequently, these units are now all defined as multiples of seconds. Units of time based on orders of magnitude of the second include the nanosecond and the millisecond. The natural units for timekeeping used by most historical societies are the day, the solar year and the