This Day in Ancient History: ante diem ix kalendas junias

Quando Rex Comitavit Fas — the rex sacrorum had to perform some sort of ceremony before the day’s legal business could be conducted (possibly connected to the idea of Regifugium)

15 B.C. — birth of the emperor-to-be-who-never-was Germanicus (brother of the emperor Claudius)

299 A.D. — martyrdom of Donatian and Rogatian