If you didn't know, atheists and some religious people like to go by B.C.E (Before the Common Era) Which goes pretty much exactly until your A.D. and the athiest's C.E. (Common Era) starts. If you're curious how it can be that exact, both Christians and Atheists use a civil calendar with the same historic origins. However, if you don't know about B.C and B.C.E. and believe that God created humans and Philosoraptors to frolic together in the fields in 0 A.D/C.E., I'm sorry for your loss in brain cells.