284 Proclaimed as emperor by the troops after the death of Numerianus, son of Carus
285 Consul suffectus II; battle of the Margus; dead of Carinus; Diocletianus is recognized by the Senate; visit to Rome; war against the Sarmatians; accepts the titles Germanicus Maximus and Sarmaticus Maximus; Diocletianus appoints Maximianus as his caesar
286 Maximianus made co-ruler; Diocletian accepts the title Iovius
287 Consul III (with Maximianus); intervention in Armenia; Maximianus fights against the Germanic tribes; Diocletian accepts the title Germanicus Maximus II and III
288 Launches an attack on the Germanic tribes, from Raetia; meeting with Maximianus; accepts the title Germanicus Maximus IV
289 War against the Sarmatians; accepts the title Sarmaticus Maximus II
Diocletian's Edict on Maximum Prices
293 Consul V (with Maximianus IV); First Tetrarchy: Galerius and Constantius I Chlorus proclaimed caesares; Diocletian's daughter Galeria Valeria marries to Galerius; all four men accept the title Germanicus Maximus, Diocletian for the fifth time; in the Sasanian Empire, Bahram II dies, and is succeeded by Bahram III, and Narseh
294 War against the Sarmatians; accepts the title Sarmaticus Maximus III; Decennalia
295 Marriage edict; Galerius fight against the Persians (?); Diocletian accepts the title Persicus Maximus
296 Consul VI (with Constantius II); Diocletian fights against the Carpi; accepts the title Carpicus Maximus and adds Britannicus Maximus after Constantius has reconquered Britain; the Sasanian king Narseh occupies Armenia; insurrection of Domitius Domitianus in Egypt
297 Death of Domitianus; he is succeeded by Aurelius Achilleus
297-298 Diocletian suppresses the rising in Egypt; sack of Alexandria
298 Galerius defeats Narseh; end of the Persian war; treaty of Nisibis (Rome gains territory east of the Tigris); Galerius and Diocletian accepts the titles Armeniacus Maximus, Medicus Maximus, Adiabenicus Maximus, and Persicus Maximus II
299 Consul VII (with Maximianus VI); Diocletian in Syria
Diocletian's palace, model
300 Accepts, after Galerius' successes along the Danube, the title Sarmaticus Maximus IV
301 Monetary reform; edict on Maximum Prizes; accepts, after Constantius' successes along the Rhine, the title Germanicus Maximus VI
303 Consul VIII (with Maximianus VII); in the Sasanian Empire, Narseh dies and is succeeded by Hormizd II; brief insurrection of Eugenius in Seleucia; edict against the Christians; Vicennalia in Rome; joint triumph with Maximianus
304 Consul IX (with Maximianus VIII)
305 Diocletian and Maximianus resign; Second Tetrarchy: they are succeeded by Galerius and Constantius I Chlorus, who appoint as caesares Maximinus Daia and Severus II
Porta Argentea, Split
Diocletian settles in Spalatum and keeps out of politics; only in 308, as consul X (with Galerius VII), he joins a conference at Carnuntum. He dies in 313.
Contemporary events
301 Gregory the Illuminator converts the Armenians
