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

Other days

slime

Slime Day
blanket fort

Blanket Fort Day
stud

Stud Day
eat what you want

Eat What You Want Day
buddy

Buddy Day
boba

Boba Day
get funky

Get Funky Day
ruby

Ruby Day
polyamory

Polyamory Day
book

Book Day