Ancient calendars 10 13, AD 10 13, BC 10 13,10/3, what's the difference?

Years are calculated from the year of A.D., which is created by modern people for the convenience of calculating ancient years, because in ancient years, emperors usually set year numbers, such as Kangxi 1 1, but there were too many ancient emperors, and each emperor would set one or more year numbers. In order to unify the calculation, there is a saying in AD .. Let's look at it this way. Long ago, we couldn't know the exact time. 10 13 or 10 13 after AD, and 10 13 or 1065438 in BC.