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

Other days

ruby

Ruby Day
bow tie

Bow Tie Day
boyfriend

Boyfriend Day
polyamory

Polyamory Day
nail polish

Nail Polish Day
ponytail

Ponytail Day
china

China Day
mean girls

Mean Girls Day
self appreciation

Self Appreciation Day
ormille

Ormille Day