idus septembres

ludi Romani (day 9)

epulum in honour of Minerva and others (connected to the ludi Romani)

ritual of the 'driving of a nail' by the Pontifex Maximus/Rex Sacrorum into the Temple of Jupiter (likely connected to the above and below entries)

509 B.C. -- dedication of the Temple of Jupiter Optimus Maximus (and associated rites thereafter; also incorporated into the ludi Romani, it seems)

490 B.C. -- yet another reckoning for the Battle of Marathon

16 A.D. -- revelation of the conspiracy of Lucius Scribonius Libo, leading to the first of the maiestas trials which characterized the emperor Tiberius' principate

81 A.D. -- death of the emperor Titus; his brother Domitian is acclaimed as emperor

122 A.D. -- construction of Hadrian's Wall begins? (I'm still wondering about the source for this claim)