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

Other days

comfy

Comfy Day
kiss a ginger

Kiss A Ginger Day
coffee

Coffee Day
first love

First Love Day
frozen yogurt

Frozen Yogurt Day
get funky

Get Funky Day
one

One Day
mean girls

Mean Girls Day
pumpkin

Pumpkin Day
gum

Gum Day