Happy Presidents' Day!
Here in the US, today's holiday is commonly referred to as Presidents Day. Or is it President's Day? Or maybe Presidents' Day? AP says don't use the apostrophe in constructions like this, unless it's an irregular noun where the plural doesn't end in S (so they approve of International Women's Day, or at least the spelling), but the Chicago Manual of Style says
Although terms such as employees’ cafeteria sometimes appear without an apostrophe, Chicago dispenses with the apostrophe only in proper names (often corporate names) that do not use one or where there is clearly no possessive meaning.Of course, the official holiday is Washington's Birthday, so there's no ruling from the government as to the official name. So, since I think it's crazy to do things differently for a noun just because it's regular, I'm using the apostrophe. Sue me.
It's a day best known for auto sales and no mail, but maybe we should take a break from the dancing Abes and Georges and think about why we're honoring them.