Christenson (2007: note 224, page 101) notes, "B'atz' is the Quiché word for the howler monkey. It is also one of the named days from the traditional highland Maya calendar." In the traditional calendar, B'atz' follows Q'anil, Toj, and Tz'i', the gods that Ixmukane invokes in her milpa ceremony (ibid, note 315, page 126).
Christenson (2007: note 311, page 125) explains the ceremony as such: "This passage likely refers to female manifestations of three of the days in the traditional highland Maya calendar—Toj, Q'anil, and Tz'i' (Ruud van Akkeren, personal communication). These are consecutive days, although the order should be Q'anil, Toj, and then Tz'i'. Modern aj q'ij priests invoke the days of the calendar in their prayers and ceremonies as lords and attribute to them specific power to bless or to punish. Thus they conceive of the days as living beings with personalities and specific spheres of influence. Toj is 'tribute or payment.' Metaphorically it may also be 'punishment or illness' caused by sin."
He continues: "In her note on Toj, as one of the named days in the traditional Quiché calendar, Ruth Bunzel quotes an aj q'ij priest collaborator: 'T'oj (enfermedad, sickness). Symbolizes the suffering which is caused by sin. ‘This is a bad day, a day of sickness. On the day t'oj one burns incense in the house for the Lord of Sickness. T'oj is also a day for calling sickness to punish an enemy. If divination comes out in 7 qanil, 8 toj, 9 ts'i' it is bad. These are bad days. The content of qanil is corn, or the milpa, toj is sickness, ts'i', 'dog,' some shameless act. When one has a sickness of the body that is like a worm eating the flesh, we call this xu jut qanil, which is a worm that is found sometimes in the milpa [maizefield]. When this worm gets into the body and eats at the flesh then it is because of these days. For this sickness comes from stealing corn or else it may be due to sorcery, for they are the days of sorcery also. For instance, if a man finds that his milpa has been robbed he goes to his milpa at midnight, breaks off an ear of corn and places a candle between the two halves, and asks San Jacinto and San Augustín, the patrons of the milpa to punish the robber, and he calls the days 7 qanil, 8 t'oj, 9 ts'i' to punish him. Then after a time the man who has stolen the corn will suffer from this disease, which is like cancer and ulcers. This is the meaning of these days' (Bunzel 1952, 282-283)."