Of the many usage errors that drive Mr. Rewrite loony, perhaps none produces as much looniness as articles and ads referring to this as President's Day weekend.
Why? It's mostly because the day honors Washington and Lincoln and has grown to cover all presidents. So if accuracy is at all important you're at least looking at the plural possessive Presidents'. But it's also because Mr. Rewrite is so terribly upset that he has to go to work Monday while Rewrite Jr. gets a day off from preschool. He's predisposed to petty, misplaced anger when this weekend rolls around.
The Associated Press Stylebook calls for Presidents Day. That's good enough for Mr. Rewrite. The New York Times Manual of Style and Usage goes with Presidents' Day. Fine with Mr. Rewrite. In Garner's Modern American Usage, Bryan A. Garner (cue angelic chorus) argues for Presidents' because the plural possessive is in order. All good, Mr. Rewrite says.
Whichever way you go on Presidents/Presidents' Day, be consistent. And never, never, never go with President's Day.
For what it's worth, a lot of Mr. Rewrite's very expensive usage guides say the plural possessive is losing favor in such cases. For example, it's the NFL Players Association, not the NFL Players' Association. AP and The New York Times go with Veterans (not Veterans') Day.
OK, let's take a deep breath and look at the carnage on Google News. Yikes. As predicted, many, many of those paid to know better are off the usage reservation.
As he noted in a string of angry tweets featuring a string of angry TwitPics, ads in Mr. Rewrite's paper batted .333 on Presidents/President's Day. If you're going to pay to have an ad in print, wouldn't you want to make sure it's stylistically correct? If you're selling print ads, which is a tough enough business these days, couldn't you build in a little more value by helping clients get the name of the holiday correct?
OK, Mr. Rewrite's going to work in the yard to redirect this burning rage. Wait – it's pouring. Maybe it's time to start getting angry in anticipation of Mother's (not Mothers) Day. Arrrrggggghhh!!!!