I've been out of the classroom for awhile but have been sort of following the transition from BC to BCE and AD to CE. It was first brought to my attention while working on the Crusader Journal, a friend of mine Joe Wolz, was writing a history article and used the BCE designator. I've not paid much attention to it as most of the history I read do not use it.
CE is Common Era and replaces AD.
BCE is Before Common Era and replaces BC.
I'm not sure any of it is necessary as the years stay the same, though it is thought that some people may object to the AD, which stands for Anno Domini, The Year of Our Lord, a reference to Jesus.
But really, if they are going to revise it they need to revise the whole damn thing (make 10s of millions of books almost impossible to use) and pick some point in the world's history that was really cool and start from there as year 1.
I vote for the founding of Sparta. Why? Because they beat the tar out of everyone and looked really, really cool doing it.