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

Other days

singles

Singles Day
boba

Boba Day
blanket fort

Blanket Fort Day
stud

Stud Day
cat girl

Cat Girl Day
mean girls

Mean Girls Day
lisp

Lisp Day
gallery

Gallery Day
bow tie

Bow Tie Day
lumpy rug

Lumpy Rug Day