There are people freaking out *right now* about how the Mayan calendar was only calculated up to the year 2012. There was even a major motion picture about how the world was destined to end.
Did anyone stop to think that the royal mathematician just got bored? Or set the "end of time" very far in the future to placate the King, who was annoying him by constantly asking "When is the world ending?". It's the Mayan equivalent of "Are we there yet?"
Or maybe he just ran out of stone tablets to carve the glyphs into.