Anno Domini

Anno Domini is a year-numbering system that counts years from the traditionally calculated birth of Jesus Christ. Its year numbers are used in the Gregorian and Julian calendars.

Dionysius Exiguus: A sixth-century monk who introduced the Anno Domini era in Easter tables. He used the era to number years in his Easter calculations.
Exiguus Easter table: Dionysius Exiguus's table of Easter dates, numbered using the Anno Domini era. This surviving calculation is the earliest known use of Anno Domini year numbering.
Gregorian calendar: A solar calendar introduced by Pope Gregory XIII in 1582 to correct drift in the Julian calendar. It is the calendar most commonly paired with Anno Domini year numbers today.
Christianization of Europe: The gradual spread and institutional adoption of Christianity across Europe. Christian institutions helped transmit a chronology anchored to Jesus's birth.
Year zero: A year numbered zero between year −1 and year 1 in some systems. Anno Domini moves directly from 1 BC to AD 1, complicating arithmetic across the era boundary.
Bede: An English monk and historian whose writings helped spread Anno Domini dating. His widely read historical works carried the system beyond its original Easter-table setting.
Julian day: A continuous count of days used in astronomy, beginning at noon on January 1, 4713 BCE. Unlike Anno Domini, it counts days continuously rather than numbering calendar years.
Chronology: The arrangement and dating of events in time. The era supplied a common framework for ordering historical events.
BC–AD dating: A system that numbers years before and after the traditional birth year of Jesus. Its paired labels distinguish years before the era from Anno Domini years.
Charlemagne: King of the Franks and emperor who ruled much of western Europe around 800. His court's adoption helped establish Anno Domini dating in western European records.

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