The Maya actually had three different versions of calendars - the Tzolk’in, the Haab', and the Calendar Round.
The first calendar was 260 days long and called the Tzolk’in. It was believed to be a religious calendar but no one knows for sure. Why 260 days? Many researchers believe that it was established in Copan – a major early Mayan site in Honduras near the Guatemalan border. It’s the time between passages of the Sun through the zenith (the point directly overhead at 90° of altitude).
The Sun is never directly overhead here in New York. It’s directly overhead exactly once if you live on the Tropic of Cancer (23.5° N latitude) on the summer solstice (because of the 23.5° tilt of the Earth’s axis). It’s directly overhead twice a year at latitudes between 0° (the equator) and 23.5° (the Tropic of Cancer). According to Wikipedia, Copan is located at 14° 50’ 24” N latitude and 089° 08’ 24” W longitude. The Sun passed through the zenith around noon on April 30 and again on August 13 in the year 426 CE (the date of the founding of Copan). The span of time from August 13 to April 30 is exactly 260 days.
While not all researchers agree with this explanation, it does work out nicely. Some have also argued that 260 days is the average number of days between the first missed menstrual period and birth (although this obviously isn’t very exact). Others have argued that it’s the number of days between planting and harvesting in agriculture (very contrived, in my opinion, since it depends on what you plant, weather, etc.).
The Tzolk’in is subdivided into 20 names of days (reflecting the vigesimal, or base-20, system of the Maya) with each day assigned a number from 1-13. This gives a total of (20x13) = 260 days. Each of the 20 names is also associated with a glyph. For example, the ninth named day is Muluk (“water”) and the glyph is shown at upper right. The fourteenth named day is Ix (“jaguar”) and the glyph is shown at lower right. Below is a table of all 20 day names and their meanings.
The way the Maya assigned names and numbers to days in the Tzolk’in calendar is complicated. It starts with Imix-1, Ik’-2, Ak’bal-3, K’an-4, … Eb-12, Ben-13, Ix-1, Men-2, …Ahaw-7, Imix-8, … Manik’-13, Lamat-1, Muluk-2, etc. In this way, every unique combination is hit.
c = A cycle from 0-19 tun (equivalent to a cycle of 20 years) – 7,200 days
d = A cycle from 0-19 k’atun (equivalent to a cycle of 20 tun) – 144,000 days
e = A cycle from 1-13 b’ak’tun (equivalent to a cycle of 13 k’atun) – 1,872,000 days
So anyway, I'll be waiting out the apolcalypse by having a few beers on Friday (or maybe I'll live it up at the end with some single malt scotch) and celebrating the solstice and the start of lengthening days (even though winter begins).