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.
DECIMUS HOSIDIUS SATURNINUS & GAIUS VIPSTANUS ASIATICUS.
MARCUS CORNELIUS SCIPIO & CNAEUS FLAVIUS ALEXANDER GERMANICUS.
OCTAVIUS FLAVIUS ALEXANDER & GNAEUS JUVENTIUS GETA
M. CLAUDIUS CAESAR AUG. DARIUS & G. ANTONIUS ERCASIUS DECIMEDIANUS