That should be AD 400. AD = anno domini = Year of Our Lord.
Thus: The Year of Our Lord, 400.
With BC (Before Christ) it's the opposite: 400 BC.
(And, yes I know that liberals like to use BCE and CE instead. Don't get me started on that)
Naah, no reason to be upset with the relabeling.
BCE = Before Christian Era.
CE = Christian Era.
:-)
Wanna keep a liberal occupied? Ask him what year Christ thought it was.
rwood