ante diem xiii kalendas quinctilias

240 B.C. — Eratosthenes calculates the circumference of the earth (I have no idea what the source for this could be)

rites at the Temple of Minerva on the Aventine

ca. 165 (?) — martyrdom of Protase

325 A.D. — Hosius announces the Nicene Creed during the First Council of Nicaea