B.C.: Before Christ
A.D. Anno Domini
CE common era
BCE: before common era
Explanation:
All of these abbreviations are used to denote time all around the world according tot he Gregorian calendar. The terms BC and Ad were commonly used by people as they are divided by the year of the birth of Jesus Christ, before it is counted backwards in BC while after is counted as AD.
To make this notation less christian the same timeline was used but it was named as Common era and before common era to not make time notation a decidedly Christian affair.
