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

Other days

eat what you want

Eat What You Want Day
frozen yogurt

Frozen Yogurt Day
ormille

Ormille Day
brow

Brow Day
self appreciation

Self Appreciation Day
ruby

Ruby Day
comfy

Comfy Day
buddy

Buddy Day
unicorn

Unicorn Day
gum

Gum Day