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

Other days

polyamory

Polyamory Day
stud

Stud Day
pampering

Pampering Day
carpenters

Carpenters Day
girl friend

Girl Friend Day
lumpy rug

Lumpy Rug Day
youth

Youth Day
boy friend

Boy Friend Day
one

One Day
promposal

Promposal Day