Codex Ixtlilxochitl is a ritual calendar that presents all the main ceremonies and holidays that were celebrated at the great teocalli, the terraced pyramid of Tenochtitlan (forerunner of present-day Mexico City) during the Mexican year. The Aztec calendar consisted of two systems. This codex presents the Xiuhpohualli (the first, or solar, calendar) of 365 days, divided into 18 months of 20 days, plus an additional period of five empty or unlucky days at the end of the year, called the Nemontemi. The manuscript begins with the first month of the year, Atlacahualco or Atlcahualo (want of water), which is represented by a drawing of a person opening his arms and bending his knees, seemingly making an offering to the sun. Each holiday is represented by a pictogram: a human form, an animal, a building, or some offerings. Under the pictogram for each holiday is a commentary in Spanish, handwritten by one of the owners of the manuscript, as a translation or explanation of the image. This document is particularly valuable, in that it includes, on folio 112 verso, a representation of the great teocalli. The series includes 21 painted images. The document is in excellent condition, as can be seen in the brightness of the colors.