Coptic calendar Roman Emperor Augustus imposed the Decree upon Egypt as its official calendar (although it was unsynchronized with the newly introduced Julian calendar which had erroneously been intercalating leap days every third year due to a misinterpration of the leap year rule so as to apply inclusive counting). To distinguish it from the Ancient Egyptian calendar, which remained in use by some astronomers until medieval times, this reformed calendar is known as the Coptic calendar. Its years and months coincide with those of the Ethiopian calendar but have different numbers and names. The Coptic year is the extension of the ancient
Gregorian calendar to number the days sequentially with no gaps, and 29 February is typically considered as the leap day. Before the 1969 revision of the Roman Calendar, the Roman Catholic Church delayed February feasts after the 23rd by one day in leap years; Masses celebrated according to the previous calendar still reflect this delay. Calendar cycles repeat completely every 400 years, which equals 146,097 days. Of these 400 years, 303 are regular years of 365 days and 97 are leap years of 366 days. A mean calendar year is days = 365.2425 days, or 365 days, 5 hours, 49 minutes and