Bede the Venerable used the expression "anno igitur ante incarnationem Dominicam" (so in the year before the Incarnation of the Lord) twice."Anno an xpi nativitate" (in the year before the birth of Christ) is found in 1474 in a work by a German monk.Eastern Orthodox countries only began to adopt AD instead of the Byzantine calendar in 1700 when Russia did so, with others adopting it in the 19th and 20th centuries.Although Anno Domini was in widespread use by the 9th century, the term "Before Christ" (or its equivalent) did not become common until much later.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).
but this date had already passed in the time of Dionysius.
Terminology that is viewed by some as being more neutral and inclusive of non-Christian people is to call this the Current or Common Era (abbreviated as CE), with the preceding years referred to as Before the Common or Current Era (BCE).
Astronomical year numbering and ISO 8601 avoid words or abbreviations related to Christianity, but use the same numbers for AD years.
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.