I have been working on a c program that ties the mayan calendar to our gregorian calendar. Running the program starting from 0.0.0.0.0 (13 baktun) on the mayan and december 21 on the gregorian, the next time 13 baktun occurs on the winter solstice is 266519 years in the future. This is exactly 52 cycles of the mayan long count calendar. The program can follow the winter solstice billions of years into the future with the mayan calendar. As the program advances into the far future the winter solstice falls at later and later dates. In 2.5 million years the winter solstice will appear around january 1st. I ran the program all day today and and the winter solstice started on december 21 2012 and went all the way around our calendar to december 21 again. I just added a counter to count the years for the full cycle. It will take another day of running to count the billions of years it will take to complete. It also keeps track of the number of cycles of the mayan calendar. Will post the results later.