Tranquillis was likely martyred during the Reign of Diocletian. There were many martyrs during the “Diocletianic Era”. The Diocletianic Era was the unusual practice of reckoning time from the start of the reign of the bitterly anti-Christian Emperor Diocletian (r. 284–305). This is in recognition of the severe persecution of the Church under Diocletian and his colleagues in rule, Maximian (r. 286-305) and Galerius (r. 305-311), although the formal universal oppression did not commence until 303, the so-called Great Oppression. Another colleague, or junior emperor, Caesar Constantius I Chlorus (r. 293-306), was conspicuous for his leniency toward Christians.