Any proof of that?
Plenty. Search "Mayan Calendar Cortez" in your favorite search engine. I use Bing.
One result on the first page says:
The calendar was also prophetic. In the 8th century A.D. it predicted that white skinned bearded gods would arrive from across the sea on March 5th, 1519. On that precise date Cortez and his conquistadors arrived in the new world.That seems reasonably unambiguous to me.