An archaeologist claims he found some gold coins dated 64 B.C.
Do you believe him?
We assume that the given problem refers to a stamped date, I.e. 64 BC, on the coin itself.
Now, people back in 64 BC did not call it so, because Jesus Christ's birth was still in the future, and they did NOT know exactly when He would be born. The years were designated as BC or AD much later than the birth of Christ.
Consequently, one should NOT believe the archaeologist as the foregoing coin MUST BE a COUNTERFEIT one.