Should I use BC and AD or BCE and CE for era designations?

The choice of era designations is up to the writer. In our publications, we prefer to use BCE (before the common era) and CE (common era), both of which follow the year:

200 BCE

300 CE

If you use BC (before Christ) and AD (anno Domini, medieval Latin for “in the year of the Lord”), note that, by convention, BC follows the year, and AD precedes it:

200 BC

AD 300