When service members move from place to place this is called a Permanent Change of Station (PCS). This process is initiated when one receives orders to a new duty station. Many times the service member can take vacation (leave) in conjunction with the move. Important considerations are the "detach date" and the "report date". The detach date is when the service member leaves his command. The report date last day for check-in at the new command.
Medical students are not authorized leave when reporting for internship.
Here is a general overview of the process:
1. Receiving new orders
2. Passing duty screening (if applicable)
3. Coordinating financial reimbursement for the move (mileage, lodging, etc)