APD question.

Does anyone know if the APD resets on your hire date OR hire month? For example: I am debating using my APD for a trip in FEB. My hire date is in March. The only other thing I might use it for is a period of time in early March (before my hire date).

Am I wasting it not using it in FEB, or will I be able to use it in early March and then get another APD after my hire date?

Thanks.