For example, the Islamic calendar begins not from the date of the Hijra, but rather weeks prior, on the first occurrence of the month of Muharram (corresponding to 16 July 622).
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.
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.
This calendar era is based on the traditionally reckoned year of the conception or birth of Jesus of Nazareth, with AD counting years from the start of this epoch, and BC denoting years before the start of the era.
The Anno Domini dating system was devised in 525 by Dionysius Exiguus to enumerate the years in his Easter table.
His system was to replace the Diocletian era that had been used in an old Easter table because he did not wish to continue the memory of a tyrant who persecuted Christians.
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.