Isn’t that “Father’s Day” and Mother’s Day,” not “Fathers’ Day” and “Mothers’ Day,” are the correct written forms?

I’m far more convinced that “Father’s Day” and Mother’s Day,” not “Fathers’ Day” and “Mothers’ Day,” are the correct written forms. Others who strictly adhere to grammatical rules, however, insist that “Fathers’ Day” and “Mothers’ Day” must be used instead based on the premise that there is not just one but more than one mother and father in the world. I believe, however, that writing “Father’s Day” and “Mother’s Day” is not only right but fitting because every single father and mother is honored on such occasions. Am I right with my conviction?