So many good things to choose from.
Anyway, the central question involving the Mayan calendar is why did they even build a calendar that has such a long period? For some people, the answer is because they knew something would happen at this point in time. That this assumption doesn't make a lot of sense is obviously no problem for some.
I still like this whole thing, though, because it made some people learn about the Mayan culture in the first place, which is a very interesting piece of history/myth. E.g. they invented the wheel, but strangely enough, there is no single evidence of it ever being used in wagons. Historians think this is because they didn't have any fitting hauling animals.