The Maya calendar can be thought of as two interlocking reels. The first "reel" was the Sacred Calendar, called the tzol'kin, with a duration of
, possibly to estimate the length of a human pregnancy. Each date on the tzol'kin was associated with powerful omens. The longer
, or haab, is so named because it's just shy of a full solar year, and includes
that aren't considered part of any month. These were known as the wayeb, or
. The haab consisted of eighteen months, each with
- the same number as their vigesimal number system.
The remarkable thing about having two calendars is how they coordinate, like a film projector. A
was a complete rotation of these two reels, and ran for about
total. A complete revolution of the haab could only align with four of the twenty days of the tzol'kin, and they align in sequence. Thus, the
system, divisions of the solar calendar, were named based on the day they began (as if we called 2001 "Monday").
In cases where they wanted to mark dates further back, the Maya employed the
. Like our own calendar, it was
and never reset. Time was not reckoned in years, but rather days, known as
. 360 of these formed a
, just shy of a solar year. The longest period of time commonly used was the
, which amounts to
. Ominously, the Maya reckoned that, since the start of creation,
of these units would have passed on December 21, 2012... and If you haven't checked the news, the doomsday prophecies for that day were quite a let-down.