Trecena 5 runs from 1 Acatl through 13 Coatl, the serpent, its span carrying reed, jaguar, eagle, vulture, movement, flint, rain, flower, crocodile, wind, house and lizard before closing on the sign that opens Trecena 9 later in the count. Sitting at the exact midpoint of the count's first third, this trecena's span crosses more named day signs with independent mythic weight than most, including three of the four year bearers' neighbours, and the tonalpouhque's tonalamatl tables would have shown this week as one of the busier stretches in terms of named associations a diviner needed to hold in mind at once.
The reed sign's own status as a year bearer means that in the separate 365 day xiuhpohualli, the solar year count, years could be named Acatl and rotate through the thirteen numbers over a fifty two year span before the full Calendar Round, the point where the 260 day and 365 day counts realign, was reached, a much longer cycle than the trecena's own short thirteen days but built from the same underlying day sign vocabulary. A reader working this trecena therefore held two calendars in view at once, the short divinatory week and the long solar year it shared a starting sign with.