Oops, it doesn't look like 'I Fucked Your Girlfriend day' is a national day..

Other days

stress awareness

Stress Awareness Day
azonto is acceptable

Azonto Is Acceptable Day
buddy

Buddy Day
cursing

Cursing Day
my little pony

My Little Pony Day
lisp

Lisp Day
prescription drug take back

Prescription Drug Take Back Day
reading

Reading Day
african immigrant and refugee hiv and hep awareness

African Immigrant And Refugee Hiv And Hep Awareness Day
boy friend

Boy Friend Day