The calendar consisted of a 365-day cycle called xiuhpōhualli (count of years) and a 260-day ritual cycle called tōnalpōhualli (count of days). These two cycles together formed a 52-year "century," sometimes called the "calendar round." The calendar is measured and counted trought the Calendar Stone (or the Aztec Sun Stone). The stone is 358 inches in diameter and 98 inches thick and weighs about 21.8 tons.
