A report on Anno Domini and Calendar era

In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era.

The Anno Domini or Common Era system, still in use with the Julian calendar and Gregorians today, marks the Incarnation of Jesus as calculated in the 6th century by Dionysius Exiguus.

Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era.

Common Era and Before the Common Era are alternatives to the Anno Domini (AD) and Before Christ (BC) notations used by Dionysius Exiguus.

In 537, Justinian required that henceforth the date must include the name of the emperor and his regnal year, in addition to the indiction and the consul, while also allowing the use of local eras.

Dionysius Exiguus proposed the system of Anno Domini in 525.

A calendar date is fully specified by the year (numbered according to a calendar era, in this case Anno Domini or Common Era), the month (identified by name or number), and the day of the month (numbered sequentially starting from 1).

Anno Mundi (from Latin "in the year of the world"; לבריאת העולם), abbreviated as AM or A.M., or Year After Creation, is a calendar era based on the biblical accounts of the creation of the world and subsequent history.

Whatever the reasons, the West eventually came to rely instead on the independently developed Anno Domini (AD) epoch system.

The world's most widely used calendar era—in which the current year is 2022 AD/CE—is based on the approximate birthdate of Jesus.

The Spanish era (Æra Hispanica), sometimes called the era of Caesar, was a calendar era (year numbering system) commonly used in the states of the Iberian Peninsula from the 5th century until the 15th, when it was phased out in favour of the Anno Domini (AD) system.