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

Other days

singles

Singles Day
donate your hair

Donate Your Hair Day
prosecco

Prosecco Day
lumpy rug

Lumpy Rug Day
cursing

Cursing Day
kiss a ginger

Kiss A Ginger Day
gum

Gum Day
mean girls

Mean Girls Day
aloxolt

Aloxolt Day
bow tie

Bow Tie Day