The Maya civilization had measured the length of the solar year to a high degree of accuracy, far more accurate than that used in Europe as the basis of the Gregorian Calendar. They did not use this figure for the length of year in their calendars, however the calendars they used were crude, being based on a year length of exactly 365 days, which means that the calendar falls out of step with the seasons by one day every four years. By comparison, the Julian calendar, used in Europe from Roman times until about the 16th Century, accumulated an error of only one day every 128 years. The modern Gregorian calendar is even more accurate, accumulating only a day’s error in approximately 3257 years.