The 819 days of the calendar must be viewed across a 45-year time period to fully understand. The movements of all major planets visible to the ancient Mayans fit into this extended calendar.

How he found the solution of the mystery of the ancient Mayan calendar, the oldest time-counting system in the world, was explained yesterday by Dr. H. J. Spinden of the Peabody Museum in an ...

The Chinese Agricultural Calendar uses lunar months to determine its dates, but it also has “solar terms” which are based on the solar year. These solar terms helped the ancient Chinese people ...