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
Julian calendar introduction of the Persian Zoroastrian (i. e. Young Avestan) calendar in 503 BC and afterwards, the first day of the year (1 Farvardin=Nowruz) slipped against the vernal equinox at the rate of approximately one day every four years. Likewise in the Egyptian calendar, a fixed year of 365 days was in use, drifting by one day against the sun in four years. An unsuccessful attempt to add an extra day every fourth year was made in 238 BC (Decree of Canopus). Caesar probably experienced this "wandering" or "vague" calendar in that country. He landed in the Nile delta in October