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

Other days

boba

Boba Day
lash

Lash Day
stud

Stud Day
polyamory

Polyamory Day
tulip

Tulip Day
pick me

Pick Me Day
self appreciation

Self Appreciation Day
blanket fort

Blanket Fort Day
coffee

Coffee Day
ask out your crush

Ask Out Your Crush Day