The Tetrarchy was the system instituted by Roman Emperor Diocletian in 293 to govern the ancient Roman Empire by dividing it between two senior emperors, the augusti, and their juniors and designated successors, the caesares. This marked the end of the Crisis of the Third Century.
The 3rd century was the period from 201 (CCI) to 300 (CCC) Anno Domini (AD) or Common Era (CE) in the Julian calendar..
The 300s decade ran from January 1, 300, to December 31, 309.
The 350s decade ran from January 1, 350, to December 31, 359.
The 240s decade ran from January 1, 240, to December 31, 249.
The 290s decade ran from January 1, 290, to December 31, 299.
Year 421 (CDXXI) was a common year starting on Saturday of the Julian calendar. At the time, it was known as the Year of the Consulship of Agricola and Eustathius. The denomination 421 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 244 (CCXLIV) was a leap year starting on Monday of the Julian calendar. At the time, it was known as the Year of the Consulship of Armenius and Aemilianus. The denomination 244 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 242 (CCXLII) was a common year starting on Saturday of the Julian calendar. At the time, it was known as the Year of the Consulship of Gratus and Lepidus. The denomination 242 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 241 (CCXLI) was a common year starting on Friday of the Julian calendar. At the time, it was known as the Year of the Consulship of Gordianus and Pompeianus. The denomination 241 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 296 (CCXCVI) was a leap year starting on Wednesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Valerius and Constantius. The denomination 296 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 293 (CCXCIII) was a common year starting on Sunday of the Julian calendar. At the time, it was known as the Year of the Consulship of Valerius and Valerius. The denomination 293 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 208 (CCVIII) was a leap year starting on Friday of the Julian calendar. At the time, it was known as the Year of the Consulship of Aurelius and Geta. The denomination 208 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 309 (CCCIX) was a common year starting on Saturday of the Julian calendar. In the Roman Empire, it was known as the Year of the Consulship of Licinianus and Constantius. The denomination 309 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 357 (CCCLVII) was a common year starting on Wednesday of the Julian calendar. At the time, it was known as the Year of the Consulship of Constantius and Iulianus. The denomination 357 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 350 (CCCL) was a common year starting on Monday of the Julian calendar. At the time, it was known as the Year of the Consulship of Sergius and Nigrinianus. The denomination 350 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Year 344 (CCCXLIV) was a leap year starting on Sunday of the Julian calendar. At the time, it was known as the Year of the Consulship of Leontius and Bonosus. The denomination 344 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
Gaius Galerius Valerius Maximianus was Roman emperor from 305 to 311. During his reign he campaigned, aided by Diocletian, against the Sasanian Empire, sacking their capital Ctesiphon in 299. He also campaigned across the Danube against the Carpi, defeating them in 297 and 300. Although he was a staunch opponent of Christianity, Galerius ended the Diocletianic Persecution when he issued an Edict of Toleration in Serdica in 311.
Byzantium under the Constantinian and Valentinianic dynasties was the earliest period of the Byzantine history that saw a shift in government from Rome in the west to Constantinople in the East within the Roman Empire under emperor Constantine the Great and his successors. Constantinople, formally named Nova Roma, was founded in the city of Byzantium, which is the origin of the historiographical name for the Eastern Empire, which self-identified simply as the "Roman Empire".
Year 420 (CDXX) was a leap year starting on Thursday of the Julian calendar. At the time, it was known as the Year of the Consulship of Theodosius and Constantius. The denomination 420 for this year has been used since the early medieval period, when the Anno Domini calendar era became the prevalent method in Europe for naming years.
