Hmm.. My history classes, German television and my 88 years old grandfather say may 8th.. Let's agree on timezone differences..? Speaking of the day the Germans signed the capitulation..
Aka: http://en.m.wikipedia.org/wiki/End_of_World_War_II_in_Europe signed may 7th, capitulation effective on my 8th.. Russia wanted a new/own capitulation later...celebrate on may 9th..