Coptic Calendar Converter

The Coptic calendar counts its years from 29 August 284, the day Diocletian took the Roman throne. That is not a tribute. The persecution he launched was the worst the Egyptian church ever endured, and the Coptic Orthodox Church chose to date its years from that wound. The era is called Anno Martyrum, the Era of the Martyrs, written A.M. So 11 September 2026 is the first of Thout, 1743 A.M. The months themselves are far older than the era. They come from the civil calendar of pharaonic Egypt, adjusted around 25 BC so that it would track the Julian year of 365 and a quarter days.

There are thirteen months. Twelve run to a flat thirty days, and the thirteenth, Pi Kogi Enavot, the little month, holds five days in a common year and six whenever the year number leaves a remainder of 3 on division by 4. The average year is therefore identical to the Julian one, which means the Coptic calendar slips roughly a day every 133 years against the Gregorian, which is the three days per four hundred years the Gregorian reform dropped. You can watch the slip in action: Coptic Christmas is 29 Koiak, which fell on 25 December in the fourth century and now falls on 7 January in most years — and on 8 January in Gregorian leap years, which is when the Coptic Church moves the celebration to 28 Koiak so the feast stays on the 7th. Nayrouz, the new year, lands on 11 September in most years, and on 12 September in the year before a Gregorian leap year.

This page runs both ways. Pick a Gregorian date at the top and you get the Coptic day, the month in its Bohairic transliteration, and the Egyptian Arabic name that farmers along the Nile still use for the seasons: Thout is also Tout, Koiak is also Kiahk. Type a Coptic day, month and year at the bottom and the Gregorian date comes back with its ISO 8601 form beside it. The arithmetic is not homemade. It comes from the browser Intl API and the ICU calendar tables that Unicode maintains. Anything before 1582 is reported as proleptic Gregorian, and the detail line says so. Two things the page will not do: it does not compute Coptic Easter or any movable feast, and it does not render the month names in Coptic script.