According to Jerome’s Chron. Tyrannus became bishop in the eighteenth year of Diocletian (301–302). If the account of Cyril’s death accepted by Harnack be taken as correct, this date is at least a year too early. If Cyril was sent to the mines in 303 and died in 306, Tyrannus may have become bishop in 303, or not until 306. According to Theodoret, H. E. I. 3, his successor, Vitalis, is said to have become bishop “after peace had been restored to the Church,” which seems to imply, though it is not directly said, that Tyrannus himself lived until that time (i.e. until 311). We know nothing certainly either about his character or the dates of his episcopate.