In remembrance of the end of World War II in Europe, https://en.wikipedia.org/wiki/End_of_World_War_II_in_Europe. Depending on where you live as to when the war in Europe ended. The unconditional surrender was signed May 7, 1945 although the ceasefire didn’t take place until May 8th or May 9th (in the Soviet Union). There were some German units that kept fighting or didn’t surrender until later. V. E. Day – https://en.wikipedia.org/wiki/Victory_in_Europe_Day.