The Maya/Aztec day-signs are very different. They are based on time and are actually names of days. Each sign lasts only one day, until it comes up again twenty days later. Like our 7-day week, which is astrological and named for the planets, the Maya and Aztecs used a 20-day week for astrological purposes.ztec/Maya Tattoo Symbolism. At the core of Mesoamerican astrology are the 20 day-signs. Like the 12 signs of the Western Zodiac, these are signs descriptive of both personality and possibility. In other words, the signs can be used to describe a person, or they can describe an event.