If there is no God then why are Mayas and Aztecs more advanced than Atheists?

Galileo was central to discovering how celestial bodies orbit and he was one of the church's biggest enemies. Einstein was an athiest and he discovered general relativity which predicts the exact orbits of planets. The Mayan and Aztec calculations were wrong which is why we have to have a leap year. Not sure what you are even referring to when you say that atheists can't come up with our own calendars.

And yet, there aren't all that many atheists tearing out beating hearts or burning heretics. Go figure.

Which one of those guys predicted the end of the world a couple of years ago with their calendar?

That sure worked out well for them.....

I have a calendar. It is sitting right on my wall. I also have one on my smart phone and another on my iPad.

There is the one true God but the native populations were pagan.