Oops, it doesn't look like 'flex on ur ex day' is a national day..

Other days

stud

Stud Day
boba

Boba Day
prescription drug take back

Prescription Drug Take Back Day
african immigrant and refugee hiv and hep awareness

African Immigrant And Refugee Hiv And Hep Awareness Day
lash

Lash Day
nae nae

Nae Nae Day
raise awerness of zeus

Raise Awerness Of Zeus Day
promposal

Promposal Day
blanket fort

Blanket Fort Day
me

Me Day