It is commonly thought that BC stands for “before Christ” and AD stands for “after death.” This is only half correct. How could the year 1 B.C. have been “before Christ” and 1 A.D. been “after death”? BC does stand for “before Christ.” AD actually stands for the Latin phrase “anno domini” which means “in the year of our Lord.” The B.C. / A.D. dating system is not taught in the Bible. It actually was not fully implemented and accepted until several centuries after Jesus’ death.
It’s people trying to get away from the religious connotations. It’s just a secularization of it. The funny thing is that it still points to the same period of time. Whether it’s called the “Common Era” or “Year of the Lord” makes no difference to me – it all still points to Christ.