This is a fine engraving of an Aztec calendar from Pre-Columbian Mexico. The Aztecs used both a 365-day calendar and a 260-day ritual calendar or almanac that was used for divination purposes. The 365-day calendar was divided into 18 months of 20 days each, plus 5 'nameless' days at the end of the year. In the 260-day cycle, 20 day names pair with 13 day numbers. The calendar is surrounded by a snake.
