Femtende april:
Global:
Art takes many forms and is an expression of many emotions, moods and events. It's a great way to demonstrate one's point of view of the world, and to process things that have happened.
So as England might have painted to process the pain of April 15th, others might use it to promote their political views, make a statement against genital mutilations, express their feelings regarding the current worldwide-situation and so on.
It was therefore prudent to celebrate the fine arts and the birthday of Leonardo da Vinci, the greatest artist of all time, was the best date for that.
Author's notes:
I don't own Hetalia