"AD & BC" vs "CE & BCE"

Everything currently being published by the Catholic Church from Encyclicals to Baptism Certificates to University Diplomas has had in clear language "Anno Domini" and will do so forever.

The reason is clear, "the church will not perish from the earth", "the gates of Hell will not prevail against it" we shouldn't "conform ourselves to this age" but remember that Jesus is with us in Spirit and Truth "even to the end of an age".

I believe the BCE is more to do with accurate representation of times.

What if (God forbid, literally) that Christianity was wiped out on Earth?

Then AD/BC wouldn't have the same meaning to people, but BCE/CE still maintains its understanding.

What if we started using the Islamic calendar?

It probably greatly offended Jews when people started using AD/BC instead of the Jewish year.

I believe the AD term is the one that primarily prompted the division. AD stands for Anno Domini, which is medieval latin for "In the Year of Our Lord". That's pretty clearly exclusive to those who believe that Jesus Christ is the son of G-d. Therefore, its widespread use ignores the beliefs of every non-Christian religion, as well as atheists and agnostics.

Use of BCE/CE is strictly a courtesy, out of respect for those whose beliefs differ from yours, and nothing more. There is no disrespect, sacrilege, or attempt to censor the government intended.

Since the actual date of Jesus' birth is in considerable dispute (I think 4 BCE is a commonly accepted date, but by no means certain), this terminology is more accurate. They're just labels for convinence: it doesn't really matter what event they're pinned on. The division of the calendar in this fashion was certainly derived from religious belief, but in common use nowadays the year number is fundamentally secular.

@Sotfware Monkey's contention that it has something to do with the separation of church and state strikes me as very odd. He's presented absoultely no evidence to back up this (to my mind) absurd claim.

I personally rather like AD/BC (and am careful to always write AD before the year number, not after), but that's just because my written English usage is conservative, even old fashioned. I'd say that this is merely matter of personal preference in writing style. It's not, really, a big deal.

It's a direct logical progression of a post-modern agnostic/atheistic (mis-)interpretation of the ideal of separation of Church and State, which thinking is, for example, twisting the US constitution from

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof

to it's "modern" interpretation of:

Government, and her officials, may in no way appear to be affiliated with nor by any means support any religious ideal or practice regardless of how beneficial to the people being governed.

In short, to be "politically correct" (social politics, not governmental), we can't be seen to endorse any religious belief in any way shape or form.

However, regardless of what label they use, the calendar is still divided with Christ's historical appearance being the center of if. While I find it a little grating, I personally don't think it's going to make much difference.

(This came up on English.SE, so part of my answer is a repost from there)

While I can't speak for all faiths, the Roman Catholic Church uses AD/BC because the epoch for the AD era is universally accepted within the Church (that is, there is no set of Catholics who hold that AD doesn't mean anything or is offensive), despite the issue of A.D. not being the year of Jesus's birth. All dates from official Roman Catholic publications use A.D./B.C.

As such, the usage of the A.D. epoch is similar to the usage of the Hebrew calendar for religious purposes in Judaism, or the use of the Hijra as the epoch for the Islamic calendar.

But while A.D. is generally used for Roman Catholics, it's not universally used with all Christian denominations, and what it signifies isn't exactly the same. For example, while A.D. 1 denotes the Christian epoch, different faiths use different calendars based on that epoch: Roman Catholics and most Protestants use the Gregorian calendar, but Eastern Orthodox churches use the Julian calendar to calculate holy days.

So 1/1/1 for Roman Catholics isn't exactly the same day as 1/1/1 for the Eastern Orthodox Churches. One side effect of this is that Easter for Roman Catholics (and most Protestants) generally falls a week before Easter for the Eastern Orthodox Churches.

Another example of differing epochs comes from the Episcopal Diocese of Maryland, which uses CE/BCE in its news publications (PDF style guide).

Going beyond who uses what, there are a few practical reasons CE/BCE is preferred in mixed company that don't have anything to do with political correctness or atheism:

Miscalculation

A.D. 1 was first calculated in the first millenium based on available knowledge at the time. Later on, it was found Jesus likely wasn't born that year, but a few years earlier (i.e., in the somewhat ironic 3–4 B.C. area). 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.

Globalization and Ecumenism

While Christians make up a very large chunk of the world's population, they are no where near the majority. 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.

However, some have co-opted CE to mean "Christian Era" instead of "Common Era". Even with this usage, it's still clear what epoch is being referred to (i.e. the Western one) without having to have some special knowledge about what "anno domini" means or who Christ is.

Calendar confusion

To the point above about the Eastern Orthodox Churches, 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. Dates in the Gregorian calendar in the Western world have always used the era designated in English as Anno Domini or Common Era, but over the millennia a wide variety of eras have been used with the Julian calendar.

Switching to CE/BCE makes it clear the Gregorian calendar is being used.

All of this isn't particularly important from a general perspective, though: it's more important to use the version most likely be understood by the audience who hears it. For most Christians (and indeed most English-speaking people), A.D. is widely synonymous with CE. At the same time, most people understand what CE means.

Simply - you participate in a bigger population, many of whom do not accept Christ (or do so as a historical figure only). Nothing more, nothing less. I don't see it as sacrilege, but personally I also don't have an opinion on the change. I'm not a believer, but AD vs CE is of little significance to me. In reality, it is exceptionally rare that I refer to things outside the last few centuries, so I rarely use any suffix.