In Nahuatl, the language of the Aztecs, it is called the Tonalpohualli or count of days.
The notion that everything consists of two opposing forces is essential to the Aztec culture. The world is always on the brink of going under in a spiritual war, a war of gods competing for supreme power. To prevent this from happening, the gods have been given their own space, their own time, their own social groups, etc, to rule over. The Tonalpohualli tells us how time is divided among the gods.
Wear the Tonalpohualli everyday to feel like an Aztec god!