Oops, it doesn't look like 'convention was held day' is a national day..

Other days

ponytail

Ponytail Day
singles

Singles Day
pick me

Pick Me Day
cursing

Cursing Day
boyfriend

Boyfriend Day
gum

Gum Day
hoodie

Hoodie Day
reading

Reading Day
kiss a ginger

Kiss A Ginger Day
bow tie

Bow Tie Day