# Mayan calendar dating system

) In ancient times, the Mayans had a tradition of a 360-day year. In one of them, they divided a 365-day year into eighteen 20-day months followed by a five-day period that was part of no month. The Mesoamerican Long Count calendar is a non-repeating, vigesimal (base-20) and base-18 calendar used by several pre-Columbian Mesoamerican cultures, most notably the Maya.The two most widely used calendars in pre-Columbian Mesoamerica, were the 260-day Tzolk'in and the 365 day Haab'.The equivalent Aztec calendars are known in Nahuatl as the tonalpohualli and Xiuhpohualli.

The length of the Tzolkin year was 260 days and the length of the Haab year was 365 days.

The smallest number that can be divided evenly by 260 and 365 is 18,980, or 365×52; this was known as the Calendar Round.

If a day is, for example, "4 Ahau 8 Cumku," the next day falling on "4 Ahau 8 Cumku" would be 18,980 days or about 52 years later.

Although there were only 365 days in the Haab year, the Mayas were aware that a year is slightly longer than 365 days, and in fact, many of the month-names are associated with the seasons; Yaxkin, for example, means "new or strong sun" and, at the beginning of the Long Count, 1 Yaxkin was the day after the winter solstice, when the sun starts to shine for a longer period of time and higher in the sky. The available evidence indicates that the Mayas estimated that a 365-day year precessed through all the seasons twice in 7.13.0.0.0 or 1,101,600 days.

When the Long Count was put into motion, it was started at 7.13.0.0.0, and 0 Yaxkin corresponded with Midwinter Day, as it did at 13.0.0.0.0 back in 3114 B. We can therefore derive a value for the Mayan estimate of the year by dividing 1,101,600 by 365, subtracting 2, and taking that number and dividing 1,101,600 by the result, which gives us an answer of 365.242036 days, which is slightly more accurate than the 365.2425 days of the Gregorian calendar.