The flag-flying day for Denmark's deployed personnel (Denmark)

A flag day is a flag-related holiday, a day designated for flying a certain flag or a day set aside to celebrate a historical event such as a nation's adoption of its flag.

Denmark is a Nordic country in Northern Europe. It is the metropole and most populous constituent of the Kingdom of Denmark, also known as the Danish Realm, a constitutionally unitary state that includes the autonomous territories of the Faroe Islands and Greenland in the north Atlantic Ocean. Metropolitan Denmark, also called "continental Denmark" or "Denmark proper", consists of the northern Jutland peninsula and an archipelago of 406 islands. It is the southernmost of the Scandinavian countries, lying southwest of Sweden, south of Norway, and north of Germany, with which it shares a short border. Denmark proper is situated between the North Sea to the west and the Baltic Sea to the east.

September 5 is the 248th day of the year in the Gregorian calendar; 117 days remain until the end of the year.