The letters generally come out about a month after the application deadline, when they've had time to run their staff over each application packet, make notes, compare assessments, mark the obvious people to accept and reject, and then agonize over the hundreds of in-between cases. The last part is, by far, the most time-consuming, as they're trying to build a balanced class of accepted students. Some years, they get a lot of science heads, and they're looking for musicians to balance the class. The next year, they have a glut of east-coast English majors, and they need mountain-state engineers and Chicago pre-law students to fill out the roster.
If you're really on eleventerhooks (that's 10% than tenterhooks), check the school's admissions page. If the info isn't there, drop a short note to the admission department; they probably have a stock reply to send you. It doesn't have to be long:
Dear Mr. Dean:
When do acceptance / rejection letters come out? I couldn't find a date on your web site, and I'm anxious to know whether I can start packing for Austin.
Apologetically yours,
Kaitlyn Frosh
