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

Other days

nail polish

Nail Polish Day
fiancee

Fiancee Day
lumpy rug

Lumpy Rug Day
youth

Youth Day
bow tie

Bow Tie Day
comfy

Comfy Day
slime

Slime Day
singles

Singles Day
ruby

Ruby Day
tulip

Tulip Day