The Mayan calendar is based on a 20-day cycle in 394-year increments known as a Baktun. On one tablet at a set of ruins in Mexico, the calendar stops at Baktun 13.

The artifact, named the 'Disk of the Pelota Players', is inscribed with a reference to a date in the Mayan calendar that is equivalent to the year 894 AD.

Characteristic of this system is the cyclical nature, with the Mayan calendar featuring three common cycles: the Long Count, Tzolk’in (260-day) and the 365-day, solar-based Haab’.

The original end-of-the-world hysteria was brought on by readings of the Mayan calendar. The calendar had an “end date,” which was believed to fall on December 21st, 2012.

Mayan calendar math is also somewhat difficult to interpret. It is based on a 260-day ceremonial cycle, the 365-day orbit of the Sun, the 584-day cycle of Venus and the 780-day cycle of Mars.

The Mayan Calendar is one of these calendars that has withstood the test of time. Although it has not been used since the civilization fell, some details are surprisingly relevant to this day.

The Mayan calendar, which spanned for about 5,125 years starting in 3114BC, reached its end on December 21, 2012. The date was hailed by conspiracy theorists as being ‘the end of the world ...

Calendar cycles were divided into “baktuns” — periods of 144,000 days — and Dec. 21 marks the day when the Mayan calendar rolls into its 13th cycle, with a date of “13.0.0.0.0.” ...

According to some interpretations of the Mayan calendar, civilization as we know it has about 11 months left. But many people in the Mayan heartland — Guatemala — see it differently.

This date is the end of the Mayan long-count period but then - just as your calendar begins again on January 1 - another long-count period begins for the Mayan calendar," the space agency explained.