The last year of the old table, Diocletian 247, was immediately followed by the first year of his table, AD 532.

Its endorsement by Emperor Charlemagne and his successors popularizing the use of the epoch and spreading it throughout the Carolingian Empire ultimately lies at the core of the system's prevalence.

According to the Catholic Encyclopedia, popes continued to date documents according to regnal years for some time, but usage of AD gradually became more common in Roman Catholic countries from the 11th to the 14th centuries.

The word “Common” in both instances refers to the date employed by the most commonly used calendar system, the Gregorian Calendar.

The years are the same, only the designations are different.

For example, the Islamic calendar begins not from the date of the Hegira, but rather weeks later, on the first subsequent occurrence of the month of Muharram (corresponding to 16 July 622).

It has also been speculated by Georges Declercq that Dionysius' desire to replace Diocletian years with a calendar based on the incarnation of Christ was intended to prevent people from believing the imminent end of the world.There is no year zero in this scheme, so the year AD 1 immediately follows the year 1 BC.This dating system was devised in 525 by Dionysius Exiguus of Scythia Minor, but was not widely used until after 800.Both Dionysius and Bede regarded Anno Domini as beginning at the incarnation of Jesus, but "the distinction between Incarnation and Nativity was not drawn until the late 9th century, when in some places the Incarnation epoch was identified with Christ's conception, i.e., the Annunciation on March 25" (Annunciation style).On the continent of Europe, Anno Domini was introduced as the era of choice of the Carolingian Renaissance by the English cleric and scholar Alcuin in the late eighth century.The Anno Domini dating system was devised in 525 by Dionysius Exiguus to enumerate the years in his Easter table.