The idea of using the year of Christ's birth as the epoch year of the Julian Calendar was first proposed by the Monk Dionysius Exiguus in 525 AD. At the time, a variety of epoch years were in common use, with the year when Diocletian ascended to the office of Emperor of Rome being the most widely used. Although the Imperial and post-Imperial Romans counted time from various reference points that changed frequently, there was one "epoch date" that was canonically (albeit infrequently) used to unify all their various time counts: the date of the founding of the city of Rome (an era that was called "Ab Urbe Condita," Latin for "From the Founding of the City.") Dionysius explicity specified the year that would be the year 1 of the Anno Domini Era as the year 754 A.U.C. ("Ab Urbe Condita.")
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