A term used to describe any group
or religious movement
(should that be predicted
?) the end of the world
order as we know it and it's replacement by the millenium
More usually they don't predict a straight out replacement but likely a period of judgement, maybe perfect justice, equality, salvation, nirvana, etc
Some sociologists I've heard think it's a symptom of a group using religion as a release valve for social pressure, also a way of delaying the pain of the 'opt out' notion by setting an arbitrary date in the future, up to which point the pains and pressures of society may be endured with grace to earn the supposed salvation, or favour of the new world order.
As the world hasn't changed radically in the years after the millenium, and more specifically didn't appear to end, a lot of these movements have died out, though some remain, most notably in Christianity, and lately, Islam. Christianity's been through two intense periods of millenarianism since its inception, while Islam has been only through one, but I imagine since Muslims use the Lunar calendar (which means their year 11 days shorter than the Solar Year) they'll catch up eventually.