I found a couple of older threads (2002ish) asking this, but they didn't really have an actual answer.
I'll be applying from out of state (school in NY), and one of the hospitals that I'm applying to wants their new grads to have their ATT in hand before they start working. Our program doesn't finish until May 20 and they plan to start their new grads on June 20. If I submit my application ASAP after finishing the program, about how long should I expect to wait to receive my ATT?