We would have known the mystery behind the Myans calendar if religious nutjobs like these didn't exist:
"Diego de Landa was a Spanish priest who visited Mexico on a charitable mission, became the Franciscan provincial of Yucatán in 1561 and is infamous for his destruction of priceless Maya documents and artefacts.
Although Landa was very interested in the Mayan culture, he abhorred certain aspects of their practices, particularly human sacrifice. In July 1562, when evidence of human sacrifice was found in a cave containing sacred Maya statues, a bout of religious self-righteousness saw Landa order the destruction of five thousand idols. He decided that their books were also the devil's work and saw to it that they were burned, with only three books surviving. Consequently the majority of Mayan knowledge and history was lost."
Google a sentence for the URL.