The Mayan calendar was used to keep track of religious days. It dates back to 5th century BC and I still in use in a few Mayan communities today.
It consists of three separate corresponding calendars and these are the Long Count, the Tzolkin (divine calendar) and the Haab (civil calendar).
The Tzolkin or divine calendar is 260-day calendar, with 20 periods of 13 days used to determine the time of religious and ceremonial events. Each day is numbered from one to thirteen, and then repeated. The day is also given a name (glyph) from a sequence of 20 day names. The calendar repeats itself after each cycle.