Field day in the Military is a thorough cleaning of an area. ie: "Field day the barracks", "field day your room". It includes dusting, mopping (swabbing) trash removal, cleaning windows, the head and organizing by military standards all manner of personal and barracks gear. Field day is no fun. The standard day in the Corps for field day wherever I was stationed was every Thurs. Field day is often followed by an inspection.
Carry on.