The Twenty Day Signs
Having looked at the basic number system, it is now possible to introduce the most important and fundamental cycle of the Mayan calendar. This is a round of twenty days that repeats perpetually. Each day corresponds to one of the numbers from zero to nineteen in the Mayan vigesimal counting system, but it also has a glyph or symbol that corresponds to it. These day signs are the key to the calendar. Each of the other cycles the Maya measured builds upon this twenty-day period. For us, the week, the month, and the year are the most familiar and important divisions of time; for the Maya, it was this repeating cycle of twenty that was paramount. They saw it as much more important than even the year.
This twenty-day cycle of time is found not just in the Mayan calendar, but also in all the Mesoamerican cultures of antiquity, including the Ol-mec, Zapotec, and Aztec. The earliest recorded inscription of these glyphs goes back to Zapotec sites San Jose Mogote and Monte Alban, which may date from between 800
Each one of the day signs not only marks a quantity of time, but also a quality of time. Each has its own specific energies and correspondences to plants and animals. Some were auspicious, others inauspicious. They were seen not just as units of measurement, but as living entities or gods. For the Maya, the twenty day signs are, in many ways, the embodiment of gods of time or the twenty faces of the sun.