Trecena 4 runs from 1 Xochitl through 13 Malinalli, grass, its thirteen days carrying the sequence through flower, crocodile, wind, house, lizard, serpent, death, deer, rabbit and water before closing on the twisted grass sign that itself opens Trecena 8 later in the round. As the fourth of twenty trecenas it sits within the count's opening quarter, and the tonalamatl tables the calendar priests consulted set its patron Huehuecoyotl beside the trecena patrons either side of it, Quetzalcoatl governing the jaguar week before it and Chalchiuhtlicue governing the reed week after, a run of three trecenas whose patrons range from the severe to the generous within the space of thirty nine days.
The numbered days within Trecena 4 each carried the patron bird system the Codex Borbonicus assigns to the thirteen numbers, a register layered atop both the trecena's own patron and the day sign's character, so that even within one artist favouring week a reader distinguished the earlier numbered days from the later ones. Because thirteen and twenty share no common factor beyond one, Xochitl itself, the day sign that opens this trecena, recurs at a different number in twelve of the other nineteen trecenas across the full 260 day tonalpohualli, never repeating its position as trecena opener until the whole count restarts.