293: Diocletian (284-305) establishes Nicomedia as one of the capitals of the roman state. Thorough fortification of the city with walls
294: Galerius Maximianus Jovius and Constantius are proclaimed caesars in Nicomedia
303: Persecutions against Christians by Diocletian
309-311: Persecutions against Christians by Maximinus (309-313)
313-324: Persecutions against Christians by Licinius (313-324)
324: Constantine I (the Great) (324-337) moves to Nicomedia
337: Constantine I (the Great) (324-337) is christened by Eusebios in the suburb of Acheron and dies at the age of 65
358-9: Destructive earthquake. Bishop Kekropios of Nicomedia among the victims.
362: Julian visits Nicomedia. Reconstruction of the city
2 December 362: Destructive earthquake
365: Valens, later emperor Valens (379-395) is proclaimed tribunus stabuli of Nicomedia
Between 364 and 378: Valens condemns to death 80 christian orthodox priests of Nicomedia
At the time of Theodosius II (408-450): Destructive earthquake. Reconstruction of the city
At the time of Zeno (479-491): Destructive earthquake
554: Destructive earthquake (post-seismic activity lasted 40 days)
At the time of Justinian I (527-565): Renovation of the public baths of Antoninus
610: Theodore of Sykeon visits Nicomedia
At the time of Justinian II (a. 685-695, b. 705-711): Nicomedia becomes the base of the military operations against the Arabs
709: Reception of pope Constantine of Rome (708-715) in Nicomedia
716: Leo III (717-741) arrests in Nicomedia the son of Theodosius III (715-717) along with the imperial escort
718: The Arabs raid Nicomedia and Nicaea during the siege of Constantinople. The Byzantines repel the enemy successfully
740: Destructive earthquake in Bithynia
26 October 746: Constantine V (741-755) arrests in Nicomedia monostrategos Niketas, son of Artabasdos (741-743), and kills him on the spot
747: Constantine V seeks refuge in Nicomedia during a plague epidemic in Constantinople
At the time of Michael II (820-829): Theodore of Stoudios moves from Chalkedon to the bay of Nicomedia
899: The hotelier of Nicomedia imposes a fine on the monasteries of the church of Nicomedia bordering the lands of the hotel at Pyles
1057: Arrival in Nicomedia of the imperial army against the rebel Isaac Komnenos
1073: Roussel de Bailleul retreats from Chrysopolis to Nicomedia
1078: The troops of the later emperor Nikephoros III Botaneiates (1078-1081) enter Nicomedia and a formal reception is organized outside the walls of the city by its strategos. Birthplace of Michael Psellos (Nicomedes)
1087: Nicomedia under the Seljuks
1096: Peter the Hermit (Pierre l’ Hermite) camps in Nicomedia on his way to Kibotus (Civetot)
1097: Transit of the crusaders through Nicomedia and arrival of the remains of the army of Peter the Hermit
End of 11th cent.: Bad weather in Nicomedia. Theofylaktos of Ohrid visits Nicomedia.
At the time of the Komnenoi dynasty (1081-1185): Fortification of the citadel of Nicomedia
1101: Transit of the crusaders through Nicomedia, which also serves as their replenishment port. Transit of William of Aquitaine (Guillaume d’ Aquitaine) through Nicomedia
1116: Nicomedia under the Byzantines
1123: Settlement of Serbs in the region of Nicomedia
1147: Transit of Conrad and his army through Nicomedia. Transit of Louis VII through Nicomedia
1179: Transit of Manuel I Komnenos (1143-1180) through Nicomedia on his way to Claudioupolis. The Latins seize Nicomedia effortlessly
1182: The suburbs of Nicomedia collaborate with the later emperor Andronikos I Komnenos (1183-1185)
March 1205: The Latins retreat from Nicomedia
Around 1205: Theodore I Lascaris (1205-1211) defeats Synadenos
1205: Nicomedia is besieged by the army of the empire of Trebizond and its outskirts are pillaged. Theodore I Lascaris (1205-1211) repels the attack
1206: The Latins seize the entire between Thynia and Nicomedia
Autumn 1206: Thierry de Los arrives in Nicomedia. Fortification of the church of Hagia Sophia
March 1207: Theodore I Lascaris (1205-1211) arrives in Nicomedia. Unsuccessful military operation of the Latins with many casualties and retreat to the church of Hagia Sophia. Theodore I Lascaris (1205-1211) negotiates the release of the prisoners in return for the fortress of the church
1211: Possible handing over of Nicomedia to the Latins
1214: Piracy obstructs transportation to and from Nicomedia
1224: John III Vatatzes (1221-1254) and the Latins sign a peace treaty in Peges, according to which the regions bordering Nicomedia remain under latin control
1246: John III Vatatzes (1221-1254) and caesar John Gavalas move to the region of Nicomedia
1255: Birthplace of Maximos Planoudes
27 July 1302: Battle in Bapheas, near Nicomedia. The Ottomans defeat the Byzantines. Kuzim Pasha is appointed governor of Nicomedia
1304: onwards: Nicomedia suffers from famine and drought due to the systematic pillage of its outskirts
1333: Nicomedia is besieged by the Ottomans. Andronikos III Palaiologos (1328-1341) negotiates with Orhan and agrees to pay 12.000 perpera each year for the fortresses of Mesothynia, from Nicomedia to Constantinople
1334: Nicomedia faces a new siege by the Ottomans with success
1337: Nicomedia under the Ottomans