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

Other days

nail polish

Nail Polish Day
singles

Singles Day
fiancee

Fiancee Day
embarrass your best friend

Embarrass Your Best Friend Day
hoodie

Hoodie Day
promposal

Promposal Day
cuddle up

Cuddle Up Day
blanket fort

Blanket Fort Day
polyamory

Polyamory Day
self appreciation

Self Appreciation Day