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

Other days

boba

Boba Day
hoodie

Hoodie Day
martini

Martini Day
cat girl

Cat Girl Day
aloxolt

Aloxolt Day
brow

Brow Day
nae nae

Nae Nae Day
pick me

Pick Me Day
girl friend

Girl Friend Day
slime

Slime Day