Date Eligible for Return from Overseas (DEROS) is issued to a United States Army Soldier or United States Air Force Airman who arrives in an overseas location. A Soldier's (Airman's) DEROS is based on which type of overseas tour they will complete and the location of the overseas tour.
A related term is "365 and a Wakeup'", first coined during the Vietnam War to annotate the length of an average tour of duty. The first number was a countdown of days left before rotating home, and the wakeup was a reference to the overnight flight that returned the soldier to the United States. If a soldier had served 10 days of a one year tour then he would say he had "355 and a Wakeup" left before he was rotated home. "365 and a Wakeup" was the title of an anecdotal book on Vietnam by Joe Pursel who served on the Naval Supervisory Group and "365 and a Wake-Up: My Year in Vietnam" by combat medic Frank Jolliff. "365 and a Wakeup" also served as the name of the most read warblog of 2004-2005 written by Dan Bout.