mil·le·nar·i·an 
(mĭl′ə-nârē-ən)
(mĭl′ə-nârē-ən)adj.
1. Of or relating to a thousand, especially to a thousand years.
2. Of, relating to, or believing in the doctrine of the millennium.
n.
One who believes the millennium will occur.
mil′le·nari·an·ism n.