What is recognized as the time in history when the calendar demarcation separating BCE from AD became official?

The term "Common Era" can be found in English as early as 1708, and became more widely used in the mid-19th century by Jewish religious scholars. Since the later 20th century, CE and BCE are popular in academic and scientific publications as religiously neutral terms.

BCE/CE in the Present Day
The use of BCE/CE in the present day, then, is not an attempt by the "politically correct" to remove Jesus of Nazareth from the calendar but has precedent in history. The usage began when people were questioning received knowledge and forming their own educated opinions about how the world worked and what constituted reliable sources. Kepler uses "vulgar era" at a time period when many institutions and understandings were being questioned and among these would have been how Dionysius arrived at his conclusions regarding the date of the birth of Jesus.

BCE/CE continues to be used because it is more accurate than BC/AD. Dionysius had no understanding of the concept of zero and neither did Bede. The calendar they dated events from, therefore, is inaccurate. The year 1 AD would follow 1 BC without a starting point for the new chronology of events. The BC/AD system, from Dionysius onward, was informed by Christian theology which took for granted that someone (Dionysius) actually knew the birth date of Jesus of Nazareth. In order to date a present event from a past event one must know when that past event occurred. One may say that one is twenty years old only if one knows for certain that one was born twenty years ago on a certain date. Dating events from an uncertain point is inaccurate because one is making an untrue statement based on a false assumption.

By the time people began questioning how Dionysius arrived at the date of Jesus' birth, or whether he was correct, over 1000 years had passed and a great deal of history had been recorded. Since there was no way to undo Dionysius' dating system, the claim that events were dated from Jesus' birth was changed to claim an event happening a certain number of years after Christian tradition supposed Jesus of Nazareth to have been born. This is more accurate in that one is not making a claim one cannot possibly support. While this dating system does refer to the same event, it does so simply out of necessity because Dionysius' system had been accepted and used for so long in written works. This dating system, like BC/AD, also has no year zero but does not need one because it is not claiming to date history from a specific event.

Aside from being more accurate, BCE/CE is inclusive. The use of BC/AD relegates every event prior to, and since, the birth of Jesus of Nazareth subordinate to the Christian understanding of who he was. For Christians, Jesus is the Christ, the anointed of God, the Messiah. The calendar "counts down" to the birth of Jesus and then proceeds to count away from it. To a Christian, this may seem like simple common sense and the way the world works but not so to someone outside of that tradition. People of different cultures and belief systems should be able to access and discuss history without having to date it according to the Christian belief in Jesus as the son of God and the Messiah.

It is for these reasons that World History Encyclopedia, following the international standard of scholarly guidelines in the 21st century, uses the designation BCE/CE instead of BC/AD. The encyclopedia has an international audience of readers who embrace multiple faiths and recognize many different belief systems. Therefore, World History Encyclopedia has adopted the BCE/CE designation in an effort to be accurate, adhere to scholarly principles, and be inclusive and welcoming to all.