Mistake number one, and of course it brings the whole house of cards crashing down, but some people can't figure that out. First of all, my alter ego, Sir Nitpick, sez it's not 33 A.D. it's A.D. 33. I'll let that pass.
But it wasn't 33 A.D. or A.D. 33. We don't know what year it was. The year 33 comes from the statement that Jesus began his public ministry when he was "about thirty years of age" and the idea that his public ministry lasted roughly three years. The three year figure comes from the mention of three different Passovers in the Gospels. But notice that both numbers are approximate; "about thirty" could mean anything from twenty-nine to about thirty-two, and the mention of three Passovers doesn't preclude the idea that there were more than three and the others simply aren't mentioned. So we have a plus-or-minus of almost ten years. And we have NO WAY to tell what year it actually happened.
But it gets even worse. We also know that our calendar is wrong. Jesus wasn't born in year A.D. 1; when the calendar was calculated, the authorities who calculated it were off by somewhere around 4-6 years. Jesus was born somewhere around 6 or 4 B.C. Again, we don't know for sure. So that gives us close to 15 years or so of uncertainty. How on earth anyone thinks they can make a precise calculation based on that, remains to be explained.
If this is how Camping arrives at his precise dates, I think it's safe to say his calculations are based on, um, NOTHING. And his followers are hanging their hats on, precisely, NOTHING.
I'd love to believe this whole movement is a joke. Sadly, it's not.