I know that we all tolerate misplaced apostrophes and that discussions on them have been done to death but I have to mention a post I just saw on a FB page for my home town. Someone has posted a poem and as a poem it's OK but it has a peculiar feature. Approximately half the plurals have apostrophes. The odd thing is that it is absolutely consistent. "Day's", "Year's", "Game's" and others are uniformly misspelled with an apostrophe while "friends", "tears" and others are uniformly correct. It is as if the author genuinely believes that some plurals have apostrophes and others don't. Odd.

Can you contact the author and ask for an explanation?

I can't help myself: Wasn't Apostrophes the Greek who invented bad grammar?

No because it is the kind of site where that would be seen as me being pedantic and aggressive. It would just call down a s##tstorm of anger on me because many posts there have similar issues.
The simple answer is that he doesn't actually realise it's wrong.

There is one time when I get mixed up with apostrophes. If I am talking about the plural of letter, like "s" I will write s's. Now with s, that's likely the way to go. It would have to be with a too, or you'll write as. But what if you write cs? And of course the context would be something like, "I have a lot of cs" when talking about my Words with Friends game.

It’s standard to use apostrophe for plurals of letters and abbreviations.

I'm inclined to write a capital letter followed by an "s" sans apostrophe. Or am I following the example of that above cited ancient Greek fellow?

Often, at least in the states, I think people consider the sans apostrophe to be the "right" way. Now, I know, we don't like to write about right or wrong here.