Cialdini talks about this in Influence. Cultists just move the date forward.

The power of belief is illustrated by the participant-observer research carried out by Festinger, Riecken and Schachter into a doomsday cult known as the Guardians, and documented in their 1956 book When Prophecy Fails. After their prediction that a flood would inundate the world and they would be carried away by spaceships did not transpire, cult members exhibited increased fervor in their beliefs. So invested were they in their beliefs that they could not risk giving them up: "The group members had gone too far, given up too much for their beliefs to see them destroyed; the shame, the economic cost, the mockery would be too great to bear" (127). In Freudian terms, their defensive behavior protected them from recognizing an unbearable truth. Cialdini explains that the moment the physical proof contradicted their beliefs, the cult members turned to the only other proof that would save them: social proof--they turned from "secretive conspirators to zealous missionaries" in an attempt to gain other converts, even though their beliefs had been shown to be baseless. "The greater the number of people who find any idea correct, the more the idea will be correct" (128). Without saying so directly, Cialdini's example of religious social proof could be considered an allegory for all the examples of millennial belief down through the ages of human civilization.