Indice
No specific reason was given for choosing the 25th of November.
In an article from The Washington Post, they speculate that it may have been because:
"That date was also the anniversary of the 1867 founding of the International Association of Chiefs of Police, the world’s first police organization, and the date in 1942 when the FBI successfully cracked the Nazis’ Enigma code machine, hastening the end of World War II."