Saeculum = 100 years

Rome Founded in 753 BC (Ab urbe condita = A.V.C.)

Emperor Claudius  celebrated 800th anniversary of Rome in 47-48 A.D with Saeculares ludi held in the Campus Martius

Emperor Antoninus Pius celebrated the 900th in 147-148

Emperor Philipus I the Millenium in 247-248