For How Many Years Have We Been Misusing the Word "Anniversary"?

By this time next year, you should be celebrating the first anniversary of using the word "anniversary" correctly.by Dave Segal Dictionary.com
To answer the question in the header: too damn many. In the realm of quixotic endeavors, trying to get people to use the word "anniversary" correctly ranks as one of the most daunting. It's up there with "hopefully" in the frequency with which it's wrongly deployed. (Even the AP Stylebook editors threw up their hands in futility over that one in 2012.)As