1) Millenarian 2) Millenarist 3) Optimist 1) Millenarist 
• (n.) One who believes in the second coming of Christ to reign on earth a thousand years; a milllenarian.
Chil'i·ast noun [ Greek .... See Chiliasm .] One who believes in the second coming of Christ to reign on earth a thousand years; a millenarian. 
chiliast Someone who believes in the coming of the millennium (a time of great peace and prosperity) when Christ returns to earth.