A Word, Please: 'Because the style guide says so!'

In two weeks’ time, Brent’s and Roy’s wives will test the limits of Brent and Roy’s friendship.

No, that’s not my pitch for the world’s lamest movie of the week. It’s a sentence designed to showcase two types of possessives that can confound even the most apostrophe-savvy writer.

Most everyone knows that apostrophes form possessives, Joe’s house, and contractions, Joe’s here. But that knowledge alone may not be enough to explain why you often see an apostrophe in two weeks’ time or why sometimes pairs like Brent and Roy share one apostrophe and other times Brent and Roy each get their own. For this, you need more than just the basics and a logical mind. You should know some tricks of the editing trade that are summed up in the terms “quasi-possessive” and “shared possessive. “

If you don’t stop and think about it, you might write “two weeks’ time” automatically, including the apostrophe, just because it “looks right.” And in fact you would be right. But if you stop and think about it, that could trip you up. The weeks aren’t really the owners of the time. So why, you might wonder, is “two weeks” in some cases written as a possessive?

To find out, you could spend hours researching something called the “genitive case,” its history and gradual fading from the English language, and how “Tim’s hat” relates to “the hat of Tim.” Or you could just answer your “why” question with the much simpler “because the style guides say so, that’s why.”

The “AP Stylebook” calls “two weeks’ time” a quasi-possessive. It doesn’t define the term, really. It just describes quasi-possessives as “such phrases as ‘a day’s pay,’ ‘two weeks’ vacation,’ ‘three days’ work,’ ‘your money’s worth.’”

“The Chicago Manual of Style” lists them under “Particularities of the Possessive” under the subheading “Genitive.” Chicago’s advice is basically the same as AP’s: “Analogous to possessives, and formed like them, are certain expressions based on the old genitive case. The genitive here implies “of”: an hour’s delay; in three days’ time; six months’ leave of absence.”