Googled this guy and a lot of the Calvinist/Pentecostal types are furious with him. He's essentially dictated that anyone still belonging to those denominations since his last failed prediction are doomed. His math is presented here--
http://www.writeonnewjersey.com/2010/02/countdown-to-judgment-2/ --for anyone who cares to check:
"[There] are 722,500 days between Jesus’ crucifixion and his return on May 21, 2011. 722,500 is the product of two repeating sets of spiritually significant numbers:
5 x 10 x 17 x
5 x 10 x 17."
So there you have it.
Here are the significant numbers, religiously, as near as I can tell from the Bible:
3 -- Minimum non-degenerate group that cannot have a tie stalemate on a decision. Hence the triumvirate or tribunal achieves a mystical power in the memespace of the ancients, who forget the original rationale as to the number and just treat it as awesome, forgetting why.
5 -- Number of fingers, originally due to number of phalanges on some ancient fish's fin.
7 -- Number of visible heavenly bodies to the naked eye*, and thus number of days in the week.
10 -- Number of fingers
12 -- Rough number of lunar cycles per year, where lunar cycle is, coincidentally, roughly 4 * size of week.
13 -- 12 + Jesus
1,000 -- "A lot," in a base 10 (fingers) counting system.
10,000 -- "A whole lot" in a base 10 (fingers) counting system.
144,000 -- "A whole hell of a lot", 12 x 12 x 10,000.
Don't see any 17s in there.
* Yes, I know technically Uranus is visible to the naked eye (no jokes, please. Or jokes, of you prefer.) but no ancient culture ever discovered it.