Officer of the day

The officer of the day (OOD), at smaller military installations where no provost marshal has been assigned, is a detail rotated each day among the unit/post's commissioned officers to oversee security, guard, and law enforcement considerations. Even if the officer has never served as an MP or is not qualified to serve as a provost marshal, officer qualification includes basic familiarity with this position.

In the Royal Navy, and other navies based upon this structure, the OOD has been delegated authority from the Commanding Officer of a ship or establishment to ensure the routine running of the vessel is carried out. Unlike the USN's OOD, the Officer of the Day is primarily a position used when a warship is alongside in port. Other duties include ceremonial duties (such as carrying out Colours or Sunset) and taking charge in emergency situations in Damage Control Headquarters. Whilst the OOD may be outranked by more senior officers on board, he or she is technically only subordinate to the Captain and the Executive Officer whilst carrying out his or her duties, but a prudent junior officer always seeks advice. Generally on warships, the OOD will be a commissioned junior officer who holds a Harbour Watchkeeping Certificate. On shore establishments, Warrant Officers may be used to augment the duty roster.

General officer of the day
In the American Civil War, a General officer of the day was a general officer assigned the duties of responding to reports by the picket line, such as a flag of truce.