section_path: Calendar era
section_name: Calendar era
paragraph_text: Calendar era
  
  The Anno Domini (AD) year numbering was developed by a monk named Dionysius Exiguus in Rome in AD 525 (AUC 1278), as a result of his work on calculating the date of Easter. Dionysius did not use the AUC convention, but instead based his calculations on the Diocletian era. This convention had been in use since AD 293, the year of the tetrarchy, as it became impractical to use regnal years of the current emperor. In his Easter table, the year AD 532 (AUC 1285) was equated with the 248th regnal year of Diocletian. The table counted the years starting from the presumed birth of Christ, rather than the accession of the emperor Diocletian on 20 November AD 284 or, as stated by Dionysius: "sed magis elegimus ab incarnatione Domini nostri Jesu Christi annorum tempora praenotare" ("but rather we choose to name the times of the years from the incarnation of our Lord Jesus Christ"). Blackburn and Holford-Strevens review interpretations of Dionysius which place the Incarnation in 2 BC, 1 BC, or AD 1.
  
  The year AD 1 corresponds to AUC 754, based on the epoch of Varro. Thus: