You are from the moment the funds are issued. You are responsible for the interest on an unsubsidized Stafford loan for the life of the loan. You still get a grace period, but the government will not pay the interest for you on the unsubsidized Stafford loan. The interest that accrues will be added to the principal balance. In essence, you will owe more than what you borrowed.
Some lenders capitalize quarterly, others annually and some only once upon repayment.
A deferment is granted by the holder of your loans and allows you to temporarily stop making payments. Deferments are not automatic, so be sure to keep paying your loans until you are notified of a decision by your lender or servicer. Like a deferment, a forbearance is granted by the holder of your loans and allows you to reduce your student loan payments or temporarily stop making payments. You must contact your lender or servicer for a forbearance form. Make sure to keep paying your loans until you are notified of a decision by your lender or servicer.