Essentially most characters would only need to know things between 50CE through to the current time.
AeRo is mostly AU after Caligula. However, the births of a few important dates were put in place to assist in working out ages, etc.
DRUSUS CLAUDIUS CAESAR AUG. (III) & LUCIUS VITELLIUS.
QUINTUS FLAVIUS CAESAR ALEXANDER & FAUSTUS CORNELIUS SULLA FELIX
MARCUS RUFIUS HONORIUS CAESAR (I) & GAIUS MARIUS FLAMINIUS