The answer
Our Church actually uses the Coptic calendar, which is based on the ancient Egyptian calendar, and is also known as the Alexandrian calendar. In 238 B.C., during the era of Ptolemy III, which precedes both calendars, the Julian (approximately 100 B.C.) and the Gregorian (16th century A.D.), a revised version of the Coptic calendar was introduced in order to calculate a leap year every fourth year. The Egyptian priests initially rejected this reformed calendar, but it became the official calendar in 25 B.C., and was synchronized with the new Julian calendar.If you like to read more, please see: https://en.wikipedia.org/wiki/Coptic_calendar
Answered by His Eminence Metropolitan Youssef (opens in a new tab)