From Academic Kids
In the armed forces, leave is permission to be away from one's unit for a period of time.
United States Military
In the U.S. military, all personnel are granted 30 days of leave per year. This time is usually used for vacations and other extended time periods away from the service that are longer than three days or need to be taken in the middle of the week.
Shorter periods of personal time away from the service are usually covered by passes, which are normally granted for normal off-duty hours and sometimes for 72 consecutive hours ("three-day-pass") as a special reward.
The day a person goes on leave is not counted as a leave day, so someone who takes short leaves can have a little more time off than someone who takes long contiguous leaves. Leave time will "roll over" from year to year. If a person leaves the service without having used all his or her leave time, the unusued days are paid for at the soldier's regular rate of pay upon separation. Conversely, though the situation is less common, pay will be deducted as excess leave on separation if too many days were taken.