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.
QUINTUS SENTIUS GEMINUS & MARCUS VELLEIUS MILO.
TITUS IMPERIUS ACUELO GURGES & LUCIUS FONTEIUS CAPITO.
GNAEUS IMPERIOS ACUELO & AULUS SALVIUS OTHO.
QUINTUS FLAVIUS CAESAR ALEXANDER AUG. & OCTAVIUS FLAVIUS ALEXANDER.