Nurse Corps Loan Repayment

1 Hoping to get some clarification from anyone familiar with the Nurse Corps Loan Repayment program. I'm currently a nursing student that works as a PCA in one of the approved hospitals. I have a job lined up when I graduate which is August of 2016. Let's say I apply in January of 2017 for the program and get accepted. When would the two year contract start? Would they retroactively count from August when I started as an RN, or does it start once you're accepted or once funds are released? Anyone who has been through this program that could give me some insight would be greatly appreciated.
Thanks!