This tool converts dates between the Gregorian calendar and the Coptic calendar (Anno Martyrum / A.M.), the liturgical calendar of the Coptic Orthodox Church still used in Egypt and Ethiopia. It is useful for finding Coptic feast dates, reading historical documents, or simply understanding a Coptic date. Conversions run both directions and are exact.
How it works
The Coptic year has 12 months of 30 days plus a short 13th month, Nasie (the epagomenal days), of 5 days — or 6 in a leap year, which occurs when the Coptic year mod 4 equals 3. Years are counted in the A.M. era, which begins in AD 284. To stay exact, the converter routes every conversion through the Julian Day Number (JDN), a continuous count of days, using the standard Coptic epoch where JDN 1825030 = 1 Tout 1 A.M. This makes the mapping fully deterministic with no calendar drift.
Example
The Coptic New Year 1 Tout 1741 A.M. converts to 11 September 2024 in the Gregorian calendar. Going the other way, entering 11 September 2024 returns 1 Tout 1741 — the first day of the Coptic month list (Tout, Baba, Hator, …, Mesra, then Nasie).
It is privacy-first: every calculation happens locally in your browser and nothing is ever sent anywhere.