In the central figure of the monument then it is not a question of the simple representation of the star of day; it treats rather of the chief chronological cycle of the aboriginal cultures, the true century or age of the Indians, as Sahagún tells us. The artist attempted to indicate, and in this face of an old man does perfectly indicate, a huehuetiliztli, a double xiuhtlalpilli: 104 years. The thought could not be better coneived nor better expressed.
Let us add that below the arrow there is another numeral; but it is not as large as the previous four, nor is it worked out in exactly the same way. Without doubt it should not be computed in the same fashion.
Let us consider the following circle, which is the third of the relief. Its description offers no difficulties, and its interpretation is the ABC of archaeological studies. It contains the twenty characters of the native month, symbols which—as they constitute the foundation of the calendars of the Nahua, Maya, Zapotec, Matlatzinca, and other races which vary in the designative terms, agreeing in the roots—we ought to consider as a common legacy from a civilizing population which served as a trunk to all the others. The signs begin with Cipactli and end with Xochitl. Mrs. Nuttall sees in these characters symbols of the native zodiac, and we do not consider the idea (suggested previously, more or less explicitly, by Boturini, Veytia, Fábrega, Orozco y Berra, del Paso y Troncoso and Chavero) absurd. The order is that well known from the monuments and the codices, to-wit:
| Cipactli | Miquiztli | Ozomatli | Cozcacuáuhtli |
| Ehécatl | Mázatl | Malinalli | Ollin |
| Calli | Tochtli | Acatl | Técpatl |
| Cuetzpallin | Atl | Océlotl | Quiáhuitl |
| Cóatl | Itzcuintli | Cuáuhtli | Xóchitl |
We may add that the style of the Cipactli appears here a somewhat peculiar one. Supporting themselves on this circle, and dividing the following one, display themselves four magnificent rays or pointers with curved base, which by their position indicate the principal divisions of the day: midday (Nepantla Tonatiuh), midnight (Yohual-nepantla), the hour of sunset (Tonaqui Tonatiuh), and that of dawn (Iquiza Tonatiuh). Gama established this symbolism.
Alternating with these, but less in size an with support upon the following circle, are other four rays, but with base not curved but
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