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TheEra of the Martyrs (Latin:anno martyrum), also known as theDiocletian era (Latin:anno Diocletiani), is a method of numbering years based on the reign ofRoman EmperorDiocletian who instigated thelast major persecution against Christians in the Empire. It was used by theChurch of Alexandria beginning in the 4th century AD and it has been used by theCoptic Orthodox Church of Alexandria from the 5th century until the present. This era was used to number the year inEaster tables produced by the Church of Alexandria.

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

Theanno Diocletiani era was not the only one used by early Christians. Western Christians were aware of it but did not use it. Most Roman Christians, like the pagan Romans before them, designated their years by naming the two consuls who held office that year.

The Romans also used theab urbe condita (AUC) era. Its name is Latin for "from the founding of the City (Rome)". However, the AUC era was hardly ever used outside historical treatises.

Eras that began at Creation, calledanno Mundi eras, became the dominant method of numbering years in the East until modern times, such as in theByzantine calendar.Annianus of Alexandria, a monk whoflourished at the beginning of the 5th century, placed the epoch of his world era on 25 March 5492 BC by counting back eleven 532-yearpaschal cycles fromanno Diocletiani 77, itself four 19-yearlunar cycles afteranno Diocletiani 1. Regarded as a civil rather than a religious era, it began on the first day of the Alexandrian year, 29 August 5493 BC. This Alexandrian era was the preferred era used byByzantine Christians such asMaximus the Confessor, until the 10th century when the Byzantine era, which had an epoch of 1 September 5509 BC, became dominant. Both eras used a version ofdating Creation based on theSeptuagint.

WhenDionysius Exiguus, anEastern Roman ofScythia Minor, inherited the continuation of those tables for an additional 95 years (in the year 525 AD) he replaced theanno Diocletiani era with one based on thebirth of Christ: theanno Domini era. His main goal was to marginalize the memory of a tyrant who persecuted Christians.^[1] Theanno Domini era became dominant in the Latin West but was not used in theGreek East until modern times.

• Adoption of the Gregorian calendar
• Calendar era
• Christian martyrs
• Computus
• Coptic calendar
• Greek East and Latin West
• Martyr

• Herbermann, Charles, ed. (1913). "Dates and Dating".Catholic Encyclopedia. New York: Robert Appleton Company. (alternate link)

• Classical antiquity
• Calendar eras
• Christian terminology
• Chronology
• Diocletianic Persecution
• Christianity in Egypt

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