Oops, it doesn't look like 'flag to commemorate historic day' is a national day..

Other days

gum

Gum Day
self appreciation

Self Appreciation Day
emoji

Emoji Day
camera

Camera Day
prescription drug take back

Prescription Drug Take Back Day
kale

Kale Day
self care

Self Care Day
tell a fairytale

Tell A Fairytale Day
unicorn

Unicorn Day
ride the wind

Ride The Wind Day