The Dominate or late Roman Empire was the "despotic" later phase of government, following the earlier period known as the "Principate", in the ancient Roman Empire. It may be considered to begin with the beginning of the reign of Diocletian in 284 after the Third Century Crisis of 235–284, and to end with the collapse of the Western Empire in AD 476, or with the reign of Justinian I (527 to 565) or of Heraclius (610 to 641). In the Eastern half of the Empire, and especially from the time of Justinian I, the system of the Dominate evolved into autocratic absolutism.