Get Ready To Have Your Minds Not Blown: The Years AD 600-900 Never Happened!
So claims a theory that says there was some kind of conspiracy to move from AD 599 to 901 AD, and so calenders were just manipulated, and some historical figures (like Charlemagne) were invented out of whole cloth to fill in the missing three centuries of "Phantom Time."
Sorry, I just thought this was too weird not to put in a main post.
Upside: This explains why the world didn't end in 2012 -- because it's not 2012. It's 1712.