What famous public holiday celebrates the events that led to the closing of the Grini prison camp? 
Grini detention camp: Grini prison camp (Norwegian: "Grini fangeleir" , German: "Polizeihäftlingslager Grini" ) was a Nazi concentration camp in Bærum, Norway, which operated between 1941 and May 1945. Victory in Europe Day: Victory in Europe Day, generally known as V-E Day, VE Day or simply V Day, was the public holiday celebrated on 8 May 1945 to mark the formal acceptance by the Allies of World War II of Nazi Germany's unconditional surrender of its armed forces. Victory in Europe Day:  It thus marked the end of World War II in Europe.
Victory in Europe Day