); the latter means “in the year of the lord,” often translated as “in the year of our lord.” (It was thought when the AD dating system was created that its year 1 was the year Jesus of Nazareth was born.) was the first of these to appear.Prior to the 6th century AD, many Christians who didn’t use an Anno Mundi (in the year of the world) type system relied on Roman dating, either marking dates from the year legend had it that Romulus and Remus founded Rome (753 BC) or by relying on the date system established under the Roman emperor Diocletian (244-311), based on the accession of Diocletian.In any event, Easter was/is the most important holy day of the Christian tradition, and it was decided at the First Council of Nicaea (AD 325) that it should occur each year on the Sunday following the first full moon after the spring equinox.In order to forecast when exactly the holiday fell each year, Easter tables were created.Most organizations and political entities, for the sake of convenience, have adopted the Western calendar, but "Anno Domini"/"Before Christ" are meaningless terms.Replacing it with "Common Era"/"Before Common Era" reinforces the notion of a global, common epoch starting at the height of the Roman Empire.Whatever the case, both it and BCE (Before the Common Era) definitely appeared in Rabbi Morris Jacob Raphall’s The use of BCE and CE was particularly popular in the Jewish community where they were keen to avoid using any nomenclature explicitly referring to Christ as “the lord.” Today, BCE and CE instead of BC and AD has become fairly common among other groups for similar reasons.When I was a kid, I was always taught to refer to years using BC (Before Christ) and AD (Anno Domini / year of our Lord). That is, BC is usually understood to mean "Before the Common Era" and CE to mean "Common Era," though it is possible to reinterpret the abbreviations as "Christian Era." The simplest reason for using BCE/CE as opposed to AD/BC is to avoid reference to Christianity and, in particular, to avoid naming Christ as Lord (BC/AD: Before Christ/In the year of our Lord). Marking it as the "Christian Era" (or more commonly, the "Common Era") allows the same epoch to be used even though the best calculation for Jesus's birth has changed.
But moreover, there is only one letter of difference between the two terms, whereas with BC and AD, the terms are clearly different and I find it easier to distinguish! BCE/CE usually refers to the Common Era (the years are the same as AD/BC).In AD 525, the monk Dionysius Exiguus of Scythia Minor was working on his table to determine when Easter fell when he decided to eliminate reference to Diocletian by listing his table’s first year as Anno Domini 532, explicitly stating this was referring to the year directly following the last year of the old Diocletian-based table, Anno Diocletiani 247.How Dionysius came up with 525 years since Jesus was born at the time he was calculating his table (532 years from when the table’s dates began) isn’t clear, but he wasn’t far off the range most biblical scholars today think, with the more modern estimates tending to ring in somewhere between 6 to 4 BC for the actual birth of Christ.Wikipedia also mentions an issue with the Julian Calendar and the Gregorian Calendar historically both using AD/BC, leading to some confusion as to which calendar system is being referred to: The terms "Common Era", "Anno Domini", "Before the Common Era" and "Before Christ" can be applied to dates that rely on either the Julian calendar or the Gregorian calendar.Modern dates are understood in the Western world to be in the Gregorian calendar, but for older dates writers should specify the calendar used.