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The '''[[Coptic]] calendar''', also called the '''Alexandrian Calendar''', is used by the Coptic Orthodox Church. It is based on the Ancient [http://en.wikipedia.org/wiki/Egyptian_calendar Egyptian calendar]. Egyptians were the first to calculate time. They divided the year into 12 months, according to their knowledge of the stars. Each of the 12 months was 30 days long, and they added five more days, which they called the 'small month'. Therefore, their year became 365 days long. To avoid the calendar creep of the Ancient Egyptian calendar, a reform of the calendar was introduced at the time of Ptolemy III (Decree of Canopus, in 238 BC), which consisted in the intercalation of a 6th epagomenal (auxiliary) day every fourth year. However, this reform was opposed by the Egyptian priests, and the idea was not adopted until 25 BC, when the Roman Emperor Augustus formally reformed the calendar of Egypt, keeping it forever synchronized with the newly introduced [[Julian Calendar|Julian calendar]]. 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]] [http://en.wikipedia.org/wiki/Ethiopian_calendar], but the latter has different Amharic month names.
==The Coptic year==
At the Council of Nicaea, it became one duty of the Coptic [[Pope]] of Alexandria to determine the exact dates of Easter and to announce it to the rest of the Christian churches (see [http://www.copticcentre.com/copticsaints.html#Pope%20Demetrius%20The%20Vinedresser Pope Demetrius the Vinedresser, 3rd cent.]). This duty fell on this officate because of the erudition at Alexandria he could draw on. The precise rules to determine this are very involved, but Easter is usually the first Sunday after a full moon occurring no sooner than March 21, which was the actual date of the vernal equinox at the time of the First Council of Nicaea. Shortly before Julius Caesar reformed the calendar, the vernal equinox was occurring on the "nominal" date of March 25. This was abandoned at Nicaea, but the reason for the observed discrepancy was all but ignored (the actual tropical year is not quite equal to the Julian year of 365¼ days, so the date of the equinox keeps creeping back in the Julian calendar).
''See also'': [http://en.wikipedia.org/wiki/Computus Computus], [[Julian Calendar]], [[Revised Julian Calendar]]
==Coptic months==
