This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
The Getty Research Institute's documentation of the Aztec Calendar Stone, the large carved basalt monument bearing day signs and calendrical bands, records the physical, dated monument that anchors much of what is actually known about how the Mexica themselves depicted their calendar's structure, the tonalpohualli and its trecenas among the systems it represents.
That physical, documented monument matters for a trecena entry because it is a primary source independent of the painted almanacs, direct material evidence for how the calendar's divisions were carved and displayed publicly, and an entry records what the stone itself does and does not depict about the trecena system, distinct from and alongside what the almanac tradition says about individual trecenas.
A trecena entry therefore draws on both kinds of documented evidence where they exist, the almanac tradition's stated meanings for a given period and the calendar stone's own carved record of the system's structure, since the Getty's documentation treats the stone as a real archaeological object with its own excavation and interpretive history rather than a timeless symbol. Both are genuinely separate, complementary sources for the same calendar system.