Doomsday prediction is the oldest racket in the book... It seems this chap has forgetten part of Rule #1 of the "Doomsday Prediction Handbook"... here's an excerpt..
1. Set a date! Pick a date in the future, preferably quite soon. Setting it too soon may result in fewer disciples. Setting it too far away may result in people forgetting, or thinking that it won't affect them. Suggested time delay: About 3-5 years.
2. Suggest an 'escape clause': If x amount of people (and their money) subscribe to the prediction, then disaster may be averted. This has the neat little bonus of making any and all outcomes consistent with your prediction. If Doomsday doesn't happen, those who subscribed/believed in you think it was they who averted disaster!
3. Repeat ad nauseum: A variant of the old "If it ain't broke, don't fix it" doctrine. Caution: It is advised not to attempt this too often, since people might start to get a little suspicious. Give it a year or two (again, we recommend 3-5 years between Doomsdays) to be on the safe side.
edit: It's my mate's birthday on Friday, so perhaps if they could delay it until early Saturday morning so we don't have to face our hangovers!