Oops, it doesn't look like 'bff to my day' is a national day..

Other days

ruby

Ruby Day
bow tie

Bow Tie Day
comfy

Comfy Day
blanket fort

Blanket Fort Day
mean girls

Mean Girls Day
bubble bath

Bubble Bath Day
polyamory

Polyamory Day
promposal

Promposal Day
stud

Stud Day
slime

Slime Day