Era of the Martyrs

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.

Alternatives among early Christians

The anno 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 the ab 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, called anno Mundi eras, became the dominant method of numbering years in the East until modern times, such as in the Byzantine calendar. Annianus of Alexandria, a monk who flourished at the beginning of the 5th century, placed the epoch of his world era on 25 March 5492 BC by counting back eleven 532-year paschal cycles from anno Diocletiani 77, itself four 19-year lunar cycles after anno 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 by Byzantine Christians such as Maximus 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 of dating Creation based on the Septuagint.