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

Other days

girl friend

Girl Friend Day
cursing

Cursing Day
self appreciation

Self Appreciation Day
tulip

Tulip Day
martini

Martini Day
self care

Self Care Day
kale

Kale Day
nae nae

Nae Nae Day
book

Book Day
buddy

Buddy Day