Nope, I'm wrong. Sorry everyone! Can't always have it right unfortunately.Wait, are you wrong or is @Carmaker1?
The Mayan Long Count calendar was insanely accurate because it's aligned with celestial events and observations. The real mystery was and is how exactly they were able to accurately calculate those things as far out as they did given the level of technology they had. Scientists are pretty sure it wasn't aliens, though.
It's never aliens....until it is.