This is the name given to the Mayan calendar of 260 days.

The 260-day count is known to scholars as the Tzolkin, or Tzolk'in. It is the name bestowed by Mayanists on the 260-day Mesoamerican calendar originated by the Maya civilization of pre-Columbian Mesoamerica. The tzolk'in calendar incorporates a cycle of twenty named days with another cycle of thirteen numbers (the trecena), to produce 260 unique days.