ante diem xi kalendas maias

Parilia (a.k.a. Palilia) -- originally a festival in honour of Pales (who protected shepherds and their flock), it eventually evolved -- in the city of Rome, at least -- into a 'birthday of Rome' celebration

753 B.C. -- traditional date for the foundation of Rome

323 B.C. -- death of Alexander the Great (by one reckoning)

323 B.C. -- death of Diogenes the Cynic

43 B.C. -- pro-Caesarian forces "under" Octavian defeat the forces of Marcus Antonius at Mutina

47 A.D. -- Claudius celebrates the ludi Saeculares (?)

148 A.D. -- Antoninus Pius celebrates the 900th anniversary of Rome

248 A.D. -- Philip Arabus celebrates the 1000th anniversary of Rome