490. CAPTAINS are the officers usually selected for Officer of the Day. At small posts with a limited number of officers, this rule is deviated from, and officers of other grades are also detailed  to perform this duty. The term is usually applied to the officer in charge for the day of a regimental camp, or small military post. Field Officers of the Day, are detailed for brigades, and a General Officer of the Day may be detailed in a command composed of one division or more. Whatever the grade of the officer, the same general principles apply as to the duty to be performed.

491. The Officer of the Day has charge of the camp or garrison of the command in which he has been detailed. He receives his orders and instructions from the Commanding Officer, and transmits them to his subordinates. All the guards of the camp or post are under his general direction; all the police parties and fatigue parties, when on duty within the line of the guards, and often fatigue parties sent beyond the lines receive their orders from the Officer of the Day.

492. The Officer of the Day is responsible for the good order, cleanliness, and attention to the daily duties throughout the camp or garrison. (Reg. 577.) He reports all matters of importance to the Commanding Officer, and receives such orders as he may deem necessary to give, pertaining thereto. The prisoners in the Guard-house are under the general control of the Officer of the Day, and they can only be properly confined and released by his order or consent.

493. The Adjutant keeps the roster of officers who may be detailed for Officer of the Day. He notifies the officer of his detail the day previous, and at guard-mounting he must be present to receive the guard after inspection. If he deems it necessary he may inspect the guard in person, but usually this would not be necessary.

494. He takes his post sufficiently far in front of, and opposite the centre of the guard, to admit of its passage in review, if he so desires. When the Adjutant has completed his formation of the guard, and the inspection is ended, he closes the ranks of the guard, and causes it to "present arms," and informs the Officer of the Day: "Sir, the guard is formed." The Officer of the Day then directs the Adjutant to march the guard in review (or by flank) to its post." (Reg. 381.)

495. After the guard has moved off towards its post, he faces toward the old Officer of the Day, who should have taken post on his right, and a little to the rear, two or three paces distant; the old Officer of Day salutes, with the hand, which should be returned by the new Officer of the Day. (Reg. 383.) The old Officer of the Day gives to the new such orders as require to be transmitted with regard to the duty, and he generally accompanies the new Officer of the Day, who is required to report at once to the Commanding Officer for orders. (Reg. 403.) The two then visit the guard, and they usually arrive there before the old guard is relieved.

497. The old Officer of the Day now makes such remarks on the guard-report of the Officer of the Guard, as he may consider proper, applying usually to the manner in which the guard-duty has been performed, and calling the Commanding Officer’s attention to such changes and corrections as he may consider necessary, and to any errors he may find in the report. This report he is required to hand in to the Commanding Officer, as soon as he has been relieved. (Reg. 406.)

498. The Officer of the Day visits the guards during the day and night, at such times as he may deem necessary, to ascertain how they perform their duty. He is required to make the rounds at least once after twelve o’clock at night. (Reg. 405.) Reg. 428 specifies the manner in which the rounds shall be made. Reg. 426 directs how the Officer of the Day shall be received in the day-time; and 427 how he shall be received at night.

499. It is the duty of the Officer of the Day to communicate the countersign and parole to the Officer of the Guard, before retreat (Reg. 404), whose duty it is to transmit it to the sentinels, before twilight, or before they begin to challenge. (Reg. 410.) The Officer of the Day is one of the officers authorized to give orders to sentinels (Reg. 413), but usually he will transmit his orders through the Officer of the Guard. 

500. The Officer of the Day directs patrols and special visits of the Officer of the Guard, to particular places, with a view to the preservation of order and vigilance throughout the camp or garrison. (Reg. 586.) A good system of patrols in a command is one of the best means of preserving order, and apprehending offenders.

501. The Officer of the Day is known by the manner in which he wears his sash. It is passed over the right shoulder, and tied at the belt, under the left arm, and crosses the body diagonally. No other officer wears his sash in this way. The Officer of the Day is considered on duty for the twenty-four hours of his tour, until he is relieved. Any offense, such as drunkenness, is the more serious when committed by him during his tour of duty.

502. The Officer of the Day is never dispensed with, he must take his tour by land or sea, on the march, or on transport, and under all circumstances under which the command is placed. His duties are slightly modified according to circumstances, but he has general charge of the order and discipline of the command for the day, and the posting and instruction of the guards for the preservation of the same. Where there is no Provost Marshal, he performs the duty that usually belongs to him, and takes charge of prisoners, and arrests offenders and depredators, and has the stragglers and shirks taken care of.