NOT WHAT THAT WORD MEANS.

"This is our six-month anniversary!"
Oh my fucking gods MENSIVERSARY. It's your sixth MENSIVERSARY.
The word for a monthly recurring date is a mensiversary.
Open a godsdamned dictionary or at least understand enough fifth-fucking-grade etymology to grasp that the prefix 'ann-' is derived from the latin 'annum', as in 'annual', meaning ONCE A GODSDAMNED YEAR. THERE IS NO SUCH THING AS AN ANNIVERSARY OF ANY PERIOD OF TIME BUT A YEAR.
And I freaking GUARANTEE that if your enough of a stereotypical chick to want to celebrate monthly dates, you've seen the prefix 'mens-' SOMEWHERE and ought to have a vague grasp as to its meaning.