Religion has lots of dates but it is not an exact science. It’s not even a science. You pick your date, I’ll pick mine, and we’ll both live happily ever after. 
I wonder what the peace mongers would be saying had they experienced WWII first hand which brings up another highly relevant date, the Warsaw Ghetto Uprising. The Biblical Jews alternated between being warriors and being victims. The warrior – trouble maker – Jews were expelled from their homeland by the Romans and became victims until the Warsaw Ghetto Uprising (as far as I know) where there were serious discussions about resistance. The older folks voted for victimhood while the young ones said, “Never Again!” Would this be a better date than the Crusade?
Look it up, it’s an important date in history.
The Captain