My son told me about the new designations for BC and AD, so I had to go look it up. - There really is no difference between an AD/BC and BCE/CE system when it comes to historical dates. The year 23 AD is exactly the same as the year 23 CE, and 4004 BC is also 4004 BCE.
References to historical dates under either classification shouldn't create confusion. Major historical dates such as 1492 AD is now 1492 CE and 1776 AD is 1776 CE.
The AD/BC method of identifying historical dates is traced back to Catholic historians working in the early Middle Ages. Identifying historical dates until that point was often a complicated proposition, since different historians worked under different calendars. Converting historical dates to the standard Gregorian calendar would not have been easy, so they began using the birth of Jesus Christ as a central point.
The term BC is short for "Before Christ". Historical dates before the birth of Christ become smaller as they approach the theoretical Year Zero.
Historical dates after the birth of Christ are classified as AD, short for the Latin phrase Anno Domini, or "in the year of our Lord". Another goodie that we learned in school has become useless - and that was one of the few things I actually remembered.