Oops, it doesn't look like 'assembly as of day' is a national day..

Other days

offer

Offer Day
comfy

Comfy Day
youth

Youth Day
cat girl

Cat Girl Day
girl friend

Girl Friend Day
nail polish

Nail Polish Day
bow tie

Bow Tie Day
pick me

Pick Me Day
ride the wind

Ride The Wind Day
slime

Slime Day