Coptic, Ethiopic, Egyptian and Armenian Holidays Rules
There are three 'Egyptian' calendar systems of historical interest. The first is the set of calendars used in ancient Egypt.
Coptic Christmas

The second is the 'Coptic' calendar, used by the Copts, a Christian sect in Egypt which was cut off from contact with the rest of the Christian world after the Islamic conquests of the seventh century, and thus preserved much of the Egyptian language and calendar as they existed in the first centuries A.D.
See also: Recurrence Rules Options.