11ac The answer actually should be VE Day - but of course that would not fit - it matches VJ Day later in 1945 - I was down in Whitehall on both days celebrating !
V-DAY is a poor clue. I've never heard anybody refer to one, always VE and VJ Days. Methinks the compiler made it up. Lord knows why, there are plenty of other words that would fit.
I was only a toddler at the time of both events and my Mummy wouldn't let me join in the celebrations!