how many years ago did the aztecs develop the ritual of building altars

Direct answer: The Aztecs did not develop a single, fixed “ritual of building altars” at one specific moment in time. Altar-building and related offerings were integral to several pre-Columbian Mesoamerican religious practices and ceremonies that evolved over a long span of the Aztec period. Altars and ritual spaces appeared within broader religious systems tied to their gods, cosmology, and calendrical observances, and they continued to influence Day of the Dead traditions after the Spanish arrival. If you want a precise date range or a synthesis of scholarly perspectives, I can gather recent sources to pin down when altar-making practices as a distinct ceremonial facet became prominent within Aztec religion and how they transformed over time.