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

Other days

gum

Gum Day
tulip

Tulip Day
boy friend

Boy Friend Day
blanket fort

Blanket Fort Day
latina equal pay

Latina Equal Pay Day
kale

Kale Day
nae nae

Nae Nae Day
boba

Boba Day
believe

Believe Day
ask out your crush

Ask Out Your Crush Day