I worked somewhere that required we use them when we left for the day or if we were in meetings all day. It was rather annoying to do every single day. Now I am not at a place that requires it thankfully. I will often put one up if I leave early or if I am arriving late. Also if I am actually out of the office I will also put one up.
Go ahead to iPhone Settings > Control Center > and include Do Not Disturb While Driving. Now you are ready to manually switch your phone to vacation mode from the control center.

This. I’m surprised more people dont havent mentioned this, but this has always been my back to work routine – and sometimes if vacations overlapped, I’d find a summary email of “While you were away, X,Y,Z happened, I covered A, but you might want to check on B and C” which was always very helpful.
Later that same year, on October 8th, President Dwight D. Eisenhower issued the first "Veterans Day Proclamation" which stated: "In order to insure proper and widespread observance of this anniversary, all veterans, all veterans' organizations, and the entire citizenry will wish to join hands in the common purpose. Toward this end, I am designating the Administrator of Veterans' Affairs as Chairman of a Veterans Day National Committee, which shall include such other persons as the Chairman may select, and which will coordinate at the national level necessary planning for the observance. I am also requesting the heads of all departments and agencies of the Executive branch of the Government to assist the National Committee in every way possible."