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

Other days

blanket fort

Blanket Fort Day
ask out your crush

Ask Out Your Crush Day
first love

First Love Day
slime

Slime Day
gum

Gum Day
tulip

Tulip Day
bounce

Bounce Day
pampering

Pampering Day
ruby

Ruby Day
pumpkin

Pumpkin Day