The Mayans said no such thing. They merely made counting marks on stones which indicate the movements of the heavens. They succesfully predicted solar and planetary movements for over five thousand years.
It is a bit curious that they no longer believed they could accurately predict after that date, but the "end of the world" is only the assumed reason. Of course, if the planets stop revolving around the sun in the current order, it could be disasterous to earth's orbit. No specific reason for the failure to predict was ever given.
News 
Market Data 
Discover 
