This codex was prepared by the Indigenous residents of Nuestra Señora de la Limpia Concepción Cuetzalan, a prosperous mining town in what is now the state of Puebla, to document the antiquity of their settlement and industry in the area. The illustrations are calendrical signs, a combination of a number and a day name, which represent “year-bearers.” Each year begins on a different date in the Aztec ritual calendar, so years carry the name of their first day. Here, scribes used personified time—3 Acatl (Reed), 4 Tecpatl (Flint), 5 Calli (House), and 6 Tochtli (Rabbit)—to illustrate their community’s living legacy.