Era of the Martyrs

The Era of the Martyrs (Latin: anno martyrum), also known as the Diocletian era (Latin: anno Diocletiani), is a method of numbering years based on the reign of Roman Emperor Diocletian who instigated the last major persecution against Christians in the Empire. It was used by the Church of Alexandria beginning in the 4th century AD and it has been used by the Coptic Orthodox Church of Alexandria from the 5th century until the present. This era was used to number the year in Easter tables produced by the Church of Alexandria.

Diocletian began his reign on 20 November 284 AD, and the reference epoch (day one of the Diocletian era) was assigned to be the first day of that Alexandrian year, 1 Thoth, the Egyptian New Year, or 29 August 284 AD.