Oops, it doesn't look like 'be a piece of shit day' is a national day..

Other days

tulip

Tulip Day
kiss a ginger

Kiss A Ginger Day
bow tie

Bow Tie Day
lumpy rug

Lumpy Rug Day
singles

Singles Day
donate your hair

Donate Your Hair Day
book

Book Day
brow

Brow Day
artists

Artists Day
slime

Slime Day