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

Other days

artists

Artists Day
one

One Day
bubble bath

Bubble Bath Day
promposal

Promposal Day
gum

Gum Day
singles

Singles Day
tell a fairytale

Tell A Fairytale Day
slime

Slime Day
china

China Day
blanket fort

Blanket Fort Day