The 365-day and the 260-day calendars identified and named the days, but not the years. The combination of a solar year date and a 260-year date was enough to identify a specific date to most people's satisfaction, as such a combination did not occur again for another 52 years, above general life expectancy. To measure dates over periods longer than 52 years, the Mesoamericans devised the Long Count calendar. This calendar system was probably developed by the Olmecs and later adopted by the Maya. The use of the long count is best attested among the classic Maya, it is not known to have been used by the central Mexican cultures. The Long Count calendar identifies a date by counting the number of days from August 11, 3114 BCE in the proleptic Gregorian calendar or September 6 3114 BCE in the Julian Calendar . Rather than using a base-10 scheme, like Western numbering, the Long Count days were tallied in a modified base-20 scheme. Thus 0.0.0.1.5 is equal to 25, and 0.0.0.2.0 is equal to 40.. Who did the Mayans probably adopt the calendar system from?