the time(s) of day that a person is available, and/or willing, to text. usually defined by how late a person sleeps in, how late they stay up and how much they nap during the day.
knowing a person's texting schedule lets you almost surely get a reply when you text the person and reduces the risk of interrupting something or waking them up.
dude, lemme know your texting schedule so i don't wake you up on the weekends anymore!