Photo by Michael McCarty 
The Aztec calendar wheels have been a source of fascination for centuries.
The Aztec calendar was a variation of earlier calendars, such as the well-known ancient Mayan calendar.
Unlike the Mayan calendar, which is very precise, the Aztec system was less precise – a certain date could refer to a couple of different times in a year.
The calendar consisted of a 365-day calendar cycle called xiuhpohualli and a 260-day ritual cycle called tonalpohualli.
These two cycles together formed a 52-year calendar round.
The xiuhpohualli is considered to be the agricultural calendar, since it is based on the sun, and the tonalpohualli is considered to be the sacred calendar.
The Tonalpohualli Calendar A late 16th century or early 17th century illustration of the Aztec tonalpohualli calendar by Juan de Tovar.