The Gregorian calendar is the most widely used calendar in the world today.
For decades, it has been the unofficial global standard, adopted in the pragmatic interests of international communication, transportation, and commercial integration, and recognized by international institutions such as the United Nations.
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.
Because BC is the English abbreviation for Before Christ, it is sometimes incorrectly concluded that AD means After Death, i.e., after the death of Jesus.
However, this would mean that the approximate 33 years commonly associated with the life of Jesus would neither be included in the BC nor the AD time scales.
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.
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.
It was believed that, based on the Anno Mundi calendar, Jesus was born in the year 5500 (or 5500 years after the world was created) with the year 6000 of the Anno Mundi calendar marking the end of the world.
but this date had already passed in the time of Dionysius.
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.