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

Other days

camera

Camera Day
lisp

Lisp Day
slime

Slime Day
cat girl

Cat Girl Day
ask out your crush

Ask Out Your Crush Day
fiancee

Fiancee Day
comfy

Comfy Day
kale

Kale Day
youth

Youth Day
singles

Singles Day