In the Andes from the beginning of the Spanish conquest, colonial administrators sought to develop efficient methods of labor extraction. The study of chronological age, Indigenous tribute, and censuses reveals an uncharted chapter of this process. This article explores how chronological age mediated the relationship between the colonial state and Andeans by creating the administrative status of tributary. Andeans adjusted their precolonial notions of aging to the concept of chronological age, which they associated with the tribute regime. During the government of Francisco de Toledo, ordinances and law relied on chronological age to standardize the time frame for tribute obligations among male Andeans as between 18 and 50 years old, and this standardization shaped Andeans' life experiences. By the late sixteenth century, previous censuses and baptism records helped to make the administrative registration of age increasingly precise. Chronological age thus emerges as a key category to study the rise of Spanish colonial rule. In doing so, this study also challenges the association between the bureaucratic use of chronological age for population control and contemporary forms of state making.