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

Other days

believe

Believe Day
ponytail

Ponytail Day
bow tie

Bow Tie Day
boba

Boba Day
blanket fort

Blanket Fort Day
lash

Lash Day
youth

Youth Day
singles

Singles Day
eat what you want

Eat What You Want Day
girl friend

Girl Friend Day