245 AD – He was born Gaius Aurelius Valerius Diocletianus this year in Dioclea, near Salona. He established an autocratic government and was responsible for laying the groundwork for the second phase of the Roman Empire, which is known variously as the "Dominate" (as opposed to the Principate instituted by Augustus), the "Tetrarchy", or simply the "Later Roman Empire".
282 AD – The legions of the upper Danube proclaimed Emperor the Praetorian prefect Carus, Diocles started gaining the new emperor’s trust, obtaining the consulship in 283 and the rank of Comes domesticorum, that is commander of the cavalry arm of the imperial bodyguard.
283 AD – Carus elected his first son Carinus Augustus, left him in charge of the care of the West, and moved with Numerian, Aper, and Diocles in the East, against the Sassanid Empire.
293 AD – Further refinement followed in this year when, under the famous tetrarchy, the empire was divided into four. Towards the end of his reign, he initiated a fierce persecution of Christians throughout the empire.
286 AD – This year, the empire was split in two, with Diocletian retaining the East, and Maximian, a loyal friend, taking the West. He became the Roman Emperor this year.
305 AD – He was abdicated on the 1st day of May tis year.
313 AD – He died this year in Split.