millennium [Lat., = 1,000 years], the period of 1,000 years in which, according to some schools of Christian eschatology, Christ will reign again gloriously on earth. Belief in the millennium, based on Rev. 20, has recurred in Christianity since the earliest times. Today it is held and taught by the Adventists and some other conservative evangelical bodies. Belief in the millennium is called chiliasm by historians of the ancient church. See Judgment Day.