The Maya calendars are one of the best-documented ancient calendars. From the 4th century BCE, the Mayans maintained three dating systems: the Long Count, the Tzolkin , and the Haab. The Haab is civil calendar and has a direct relationship to the length of the year. They divided a 365-day year into eighteen 20-day months followed by a five-day period. The five- day was not a part of any month and was considered to be unlucky days.Chichen Itza located in Yucatan, Mexico was the Mayan Pyramid and was used as a calendar. It has four stairways and a platform. Each stairways has 91 steps multiply 4 plus the platform makes a total of 365. This is equivalent to the number of days in a calendar year.
For more about Maya calendar, you can check the following sites:
www.webexhibits.org/calendars/calendar-mayan.html
en.wikipedia.org/wiki/Maya_calendar