The Maya Calendar
source: https://www.museumstorecompany.com/Maya-Mayan-Calendar-p4823.html
The Maya are a group of people who lived in Mesoamerica from about 2600 BCE through the Spanish conquest of the Americas, though there are small pockets of Maya still living today in the highlands of Guatemala and Chiapas, with millions still speaking the Mayan language and who still follow the cycles of their historical calendars.
source: https://www.livescience.com/25662-how-mayan-calendar-works.html
The Maya calendar is actually three interlocking calendars that work together to give each day within the greater cycle a unique identifier. The shortest calendar is 260 days known as the Tzolkin or Tzolk'in. It is a combination of twenty day names with thirteen day numbers. The next was a solar calendar known as the Haab'. It is created by having eighteen twenty-day months with five 'unnamed' days. Combing the two, it takes 52 Haab' for the combination of the two to return back to their initial orientation. In addition to these two, there is the Long Count calendar, which is used to keep track of events that occur more often than the 52 years, or a person's lifetime at the time. There are also additions to these three that add the phase of the moon to any date.
Though the Calendar Round restarts when the initial combination is reached again, there are certain dates in the Tzolk'in that have to occur on specific Haab' days. The first day of the Haab' calendar, notated as 0 Pop, which means the 'seating of Pop', is known as the 'Year Bearer', which defines the prognostications that go with the year and which deities that are paramount. The Long Count calendar is a five section date that counts the days from the date of creation and is currently written as 0.0.0.0.0, which represents the date of creation, which is approximately 11-13 August 3114 BCE, varying depending on source. While the Maya use a base twenty system, not all of those sections go to twenty. Since the second to last section counts months, it only goes to 18 before returning to 0 and incrementing the next section up one. Once the first section is incremented, this is a 'restarting' of the calendar, or a 'b'ak'tun', which most recently occurred on 12 December, 2012 at the beginning of the 13th b'ak'tun and will next occur on 26 March, 2407, or 144,000 days later. The Long Count calendar will gain a sixth position on 13 October, 4772, or 2,880,000 days from the beginning of creation, something known as a piktun.
