Oops, it doesn't look like 'empire day' is a national day..

Other days

first love

First Love Day
cuddle up

Cuddle Up Day
blanket fort

Blanket Fort Day
my little pony

My Little Pony Day
believe

Believe Day
youth

Youth Day
tulip

Tulip Day
mean girls

Mean Girls Day
girl friend

Girl Friend Day
slime

Slime Day