Question: What famous public holiday celebrates the events that led to the closing of the Grini prison camp? 
Sentence (from "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.
Relevant evidence: Yes