May 8 is Victory in Europe Day.
This day is celebrated by many European countries and it is generally known as V Day.
The German administration headed by Hitler's successor Karl Dönitz signed the act of military surrender on May 7 in Reims, France, and on May 8 in Berlin, Germany.
The Soviet representative didn't have authority to sign the act in Reims, that is why the Soviet leadership considered the document as a “preliminary” act.
The ceremony was repeated in Berlin on May 8 and the military surrender act came into effect at 11:43 p.m. Central European Time.
In Soviet Union it was already past midnight, that is why May 9 is Victory Day in former Soviet countries