Library on Wednesday's

It seems to be an epidemic these days - those bloody misplaced apostrophes. They drive me absolutely nuts. 

You know, the concept of apostrophes isn't really that hard.  They either represent possession or indicate a contraction.  Neither of which is the case in Library on Wednesday's.  If you reversed the sentence, Wednesday's Library it might make a bit more sense.  It could mean the library owned by Wednesday, if that was somebody's name, or it could mean Wednesday is Library (day). 

But that's not what it means.  What is trying to be communicated is that Library day is on Wednesdays, as in every Wednesday.

Now I've been accused of getting my knickers in a twist about these things which, in the grand scheme of things, don't really matter that much.

But no.

This was printed on Lego Boy's classroom calendar. Written by his teacher.  The one who's supposed to be teaching him how to communicate in written English.

So knickers remain well and truly twisted.