Millennialism (from millennium, Latin for "thousand years"), or chiliasm in Greek, is a belief held by some Christian denominations that there will be a Golden Age or Paradise on Earth in which "Christ will reign" for 1000 years prior to the final judgment and future eternal state (the "World to Come" of the New Heavens and New Earth). This belief is derived primarily from the Book of Revelation 20:1–6. Millennialism as such is a specific form of Millenarianism.
Millennialism is strongly rejected as a heresy by the Orthodox Church. In AD 230, the Synod of Iconium declared that baptisms performed by the Montanist sect were invalid. The Ecumenical Council of Constantinople in AD 381 supported the Synod of Iconium and further declared millennialism to be a heresy.
http://en.wikipedia.org/wiki/Millennialism