millenarianism

Originally the millennium was not simply any thousand-year period, but instead the thousand years prophesied in the biblical Book of Revelation, when holiness will prevail on earth and Jesus Christ will preside over all. Later, millennium was extended to mean any period—always in the future—marked by universal happiness and human perfection. On several occasions over the centuries, members of Christian sects have become convinced that the biblical millennium was arriving and gathered together to await it. But nonreligious millenarians have also believed in a future society marked by human perfection. Even if they regard this future as certain, they've generally been willing to help it along by working for a political, social, or economic revolution. The millennium always seems to be approaching; to date, it hasn't arrived.