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

Other days

hoodie

Hoodie Day
cursing

Cursing Day
reading

Reading Day
ruby

Ruby Day
gum

Gum Day
self care

Self Care Day
kiss a brunette

Kiss A Brunette Day
lash

Lash Day
carpenters

Carpenters Day
first love

First Love Day