The Aztec Calendar: Math and Designs explores the inner workings of the Mexican Sun Stone. The author analyzes the central meaning to the calendar as of the different concentric rings which create its intriguing design. The knowledge about the calendar's meaning and function has been lost throughout the ages. However, its design elements suggest a certain logic of numbers. These numbers reflect the orbital times of Earth and Venus, along with other day-counts and cycles of our Universe. The author explains how the calendar's rings suggest movements to reckon the days.