Not long ago I wrote a column about how sometimes in terms like "teachers' union" and "homeowners' policy" the apostrophe is optional. If you really mean that the first noun possesses the second, an apostrophe makes sense. But if the first noun is intended as more of an adjective, you can often drop it: teachers union, homeowners policy.
The column prompted an interesting response from a reader named Mary, who wanted know how the lesson applied to a recent document she had helped produce that made reference to Founders' Day, complete with apostrophe.
"I'm thinking we made a mistake by adding the apostrophe to Founders Day. It's a once-a-year celebration like Mothers Day, which I guess doesn't need an apostrophe either. Right?"
Chalk this up to yet another example of how difficult language can be. Sometimes, it's all about interpretation. At other times, without warning, it's about rules. And though the choice between "teachers' union" and "teachers union" is based on the writer's intent, holidays don't offer as many options.
Look at Mother's Day, April Fools' Day and Veterans Day. These are all punctuated correctly. Mother's Day is singular possessive, with the apostrophe before the s. April Fools' Day is plural possessive, meaning the apostrophe comes after the s. And Veterans Day takes no apostrophe at all. And there's no way know any of these for certain without checking a dictionary or other reference book.
Most holidays are proper nouns. That means that their punctuation is part of their official spelling. The writer referencing one of these holidays isn't making the call on whether to include an apostrophe or where. Instead, the writer is just using a formal name, not unlike McDonald's or Macy's.
Most holidays are listed the dictionary. Mother's Day, Father's Day, St. Patrick's Day and Valentine's Day are all in there with the apostrophe before the s. The suggestion is that a certain day is Mother's. It belongs to her. Why does it belong to just Mother and not all mothers? No logical reason. It's simply what the lexicographers who write the dictionaries have surmised is the standard form.
Of course, it's not always that simple. A lot of people don't realize that dictionaries often disagree on matters like these. So while some would have you write Presidents' Day with an apostrophe after the s, while others might dub Presidents Day with no apostrophe as their preferred form.
Further complicating matters: Style guides sometimes disagree with dictionaries and each other. So in a publication that defers to a style guide, as most newspapers do, you may see Presidents Day with no apostrophe. But in books, which usually follow a different style guide, you'll probably see Presidents' Day with an apostrophe.
So how then did I answer's Mary's question about Founders/Founders' Day? With a loud and resounding "I don't know."
All my attempts to come up with a clear answer failed. First I checked Webster's New World College Dictionary, which is the default dictionary for many newspaper publishers. No listing. Then I checked Merriam-Webster's Collegiate, which is the choice of book publishers. Nothing. I checked the Associated Press Stylebook and the Chicago Manual of Style, neither had it. I even checked two usage guides, Garner's Modern American Usage and Merriam-Webster's Dictionary of English Usage. None of them had a word to say about it.
With no expert referee to make the call, all I could do was revert back to the less-reliable standard of simple logic. "I would go ahead and make an executive decision," I wrote to Mary. "Personally, I prefer Founders' Day."
That was her preference, too.