In the United States military, ETS generally stands for "expiration - term of service" and is contained in each service member's contract. On the ETS date, a service member's current contract has expired and the service member is free to leave the military or sign a re-enlistment contract.
A military ETS date is important for verifying veterans' benefits. It can be found on discharge papers, which are often referred to as the DD-214, along with other important information, such as discharge status, certain military honors and details about a veteran's service. The ETS is also used as an active-duty anniversary date for determining pay raise timing, tours of duty, eligibility for promotions or mandatory discharges. The ETS is not necessarily the same as a discharge date.