After years of considering data from varied fields such as astronomy, ethnography, archeology and iconography, J. Eric S. Thompson determined that 0.0.0.0.0(start of Mayan calander) correponded to the Julian date 584283, which equals August 11th, 3114 B.C. in our Gregorian calendar. This means that the end date of 13.0.0.0.0, some 5125 years later, is December 21st, 2012 A.D.1.