Before commenting on something that the AP Stylebook’s Facebook account posted yesterday, I’ll show you a grammar question I recently asked Gemini because it’s relevant in this context:

Ludditus: Which one is better?

  • a two weeks notice
  • a two weeks’ notice
  • a two-week notice (technically possible)
    I see it as “a notice of a certain kind,” not as a possessive, but some people advocate the apostrophe.

Gemini: Your instinct to view it as “a notice of a certain kind” is entirely valid, but the core issue actually revolves around the article “a” and whether you are treating “notice” as a tangible document or an abstract concept of time.

Here is the breakdown of why the grammar behaves the way it does:

1. A two-week notice (The Adjectival Approach)

If you include the article “a,” this is the only grammatically correct option of the three.

By hyphenating “two-week,” you create a singular compound adjective modifying the noun “notice.” This treats “notice” as a countable, physical document (like a formal resignation letter). Your view of it being a specific kind of notice is exactly how this structure functions.

  • Correct usage: “I handed HR a two-week notice.”

2. Two weeks’ notice (The Genitive of Measure)

Notice that the “a” is missing. If you are referring to the abstract concept of advance warning, rather than a physical piece of paper, this is the traditional and most universally accepted phrasing.

People who advocate for the apostrophe are technically correct, but it isn’t a true possessive (the weeks do not “own” the notice). It is a genitive of time or measure, an old English construction also seen in phrases like a day’s pay, an hour’s delay, or a stone’s throw.

Because “notice” in this context is an uncountable mass noun, placing “a” in front of it (“a two weeks’ notice”) causes a syntactic clash.

  • Correct usage: “I gave them two weeks’ notice.”

3. A two weeks notice (The Error)

This is grammatically incorrect. It improperly drops a plural noun (“weeks”) right in front of another noun without the necessary punctuation to explain its mechanical role—either a hyphen to bind it into a singular adjective, or an apostrophe to indicate the genitive of measure.

The Verdict

  • If referring to the physical document: a two-week notice.
  • If referring to the concept of time/warning: two weeks’ notice (drop the “a”).

Now, to the point.

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As a non-native speaker of English, I didn’t know of the so-called “genitive of time or measure.” I took it to be an illogical possessive used in certain constructions. Genitive and possessive overlap in other languages, too. (The plural “’s” and the possessive “’s” ending in Dutch can be much more confusing than in English.)

But now that I’ve learned about this particular genitive (not that I understood it, because I didn’t!), the AP Stylebook came up with a “descriptive sense” that bans an apostrophe before the final “s” in certain constructions. And this literally made me hate them!

AP Stylebook posted this on FB:

Do not add an apostrophe to a word ending in s when it is used primarily in a descriptive sense: citizens band radio, a Cincinnati Reds infielder, a Teamsters request, a writers guide.

Many of the 2.4K comments disagree that this is a general rule.

If there is a “genitive of measure” thing in English, then some of the objections might be true.

I selected and grouped some comments so I could add my quick notes on them.

§1. “a writers guide” is contested:

● A writers’ guide should surely have an apostrophe after the s. “A guide for writers” is different.

● “writers guide” seems different than the others to me too. Interesting!

● Except that this is mostly a descriptive sense. It’s not really a possession of the writers as a whole. So, in AP Stylebook style, you wouldn’t put an apostrophe. It’s not about being right. It’s about being consistent.

● OK. Good to know that as long as I’m consistent I can be wrong!

● Welcome to English. Someone will be along to correct you shortly. Wrong is in the pen of the beholder.

● Isn’t it still possessive though? Thus requiring an apostrophe? I mean, I understand the distinction, but it’s still grammatically incorrect I think, which confuses the reader IMO. I have always thought that grammar and style guides were intended to make communication clearer, not make it a bowl of spaghetti.

● If we’re talking about specific writers, yes. “Many famous writers’ guides to birding have fetched a price at auction.” If it’s describing a certain guide to writing, tho, it’s “a writers guide.”

● It’s not a possessive, it’s a more general adjective. Guide for writers, not guide that belongs to writers.

● Ew, that last one looks terrible! Maybe I am not disagreeing with the rule itself, per se, but with the inclusion of that example as something to which the rule applies. “A writer’s guide” is not a “descriptive” in the same way as these others, and even if there is no specific writer to whom the guide belongs it makes sense to treat it as a possessive, as it is a guide appropriate for ownership and use by writers, not just one connected to writers conceptually or originating from writers.

● I think I finally get it, we’re debating over whether the modifying word answers “whose thing” vs “what kind of thing”. Does that mean it should be “drivers license” since the modifier is about distinguishing from other kinds of license?

● I think that is what they are saying.

● My Michigan ID says “Driver’s License”

● Here in the UK it’s a “driving licence” which saves much discussion!

MY NOTES: People, while being native speakers, conflated the genitive and the possessive. And adding to the discussion “Driver’s License” instead of the more logical “driving license” (what kind of license?) doesn’t help. If anything, it left me even more confused as to how “a writers guide” should be written! I vote for “a writer’s guide” or “a writers’ guide”!

§2. Some people shared my pet peeve!

● What about “a few days notice”? That one has always confused me!

● Former copy editor here: It helps to think of the apostrophe taking the place of the word “of.” It is “a few days’ notice” (Days is plural here so the apostrophe comes after the s) or “he gave only a day’s notice.” (Day is singular in the second example, so the apostrophe comes before the s.) Does this make it clear?

● How does “of” help?

● A few days (worth) of notice.

● Why would days be possessive??

● The notice doesn’t belong to the that, “a few days” is how long it took to provide the notice. ‘s (or s’ if plural) is to show possession.

● The movie title was ‘Two Weeks Notice’. I held up an apostrophe on a long stick adding it to the ‘s’ on the cinema title in my town as people queued outside for the movie!

● It’s the same rule for periods of time in general. Like this:
I will let you know in three months.
I will give you three months’ notice.
I’ll be past all this in a year.
In a year’s time, I will be past all this.
Let the landlord know thirty days before you move out.
Give the landlord thirty days’ notice.

MY NOTES: I’m still mildly confused. And no, that former copy editor was of no help. The “of” trick only adds to the confusion: if it’s “a few days (worth) of notice,” does this mean we should write “a few days’ notice”? The last comment was helpful, but it only included examples without an article or a numeral: “I will give you three months’ notice.” What about “I will give you a three-month notice”? Or, “I gave them three-month notice slips”? On the other hand, “in a year’s time” is a different case because it strongly suggests possession, although a year does not possess that time! Hence my stubborn confusion.

§3. More confusion: is it a “genitive of measure,” a possessive, or “a plural in descriptive sense”?

● But what if it were describing the infielder that belongs to the Cincinnati Reds. Then the grammatically correct way would be Cincinnati Reds’ infielder.

● Pretty sure that’s the exact opposite of what they are saying here…

● Boys/Girls Basketball rather than Boys’/Girls’ Basketball (or whatever sport…) This has been an ongoing question.

● Well, is it basketball for boys? Or is it their basketball league? I would think that it’s their league and it’s Boys’ Basketball. It doesn’t belong to the girls.

● I’d say the difference is whether you look at it like a collection of people or items versus the object belonging to the group.

● Does this apply to boys and girls sports?

● I think about this a lot as a teacher: doctors note, doctor note, doctor’s note?

● What about in a term like Workers Compensation?

● I work in the workers’ compensation insurance field in New York State, and the state agency that oversees claims is the New York State Workers’ Compensation Board. So we go with that.

● Thanks. I work in insurance and that explains why workers compensation doesn’t get an apostrophe in my company.

● Farmers market?

● This one always trips me up. I’ve seen it both ways.

● Farmers’ market.

● What about a farmers’ market?

● What about Artists’ Choice and People’s Choice awards?

● Okay, but is it the attorneys fees or the attorneys’ fees?

● The attorneys’ attorneys fees?

● Like Mothers Day? And Fathers Day?

● In that case, no apostrophe because it’s a day celebrating mothers, not a day belonging to one or mothers.

● Does this apply to boys and girls sports?

● I guess I was correct in giving up on where to put the apostrophe in “writers night” long ago! It’s accurate either way.

● Nah, it’s not accurate either way, it’s just consistent with this style guide. Accurate would be writers’ if the night belonged to more than one writer.

● This prompted me to look up the song “Ladies’ Night”. It’s the same thing.

● “2026 Annual Pastors Conference”?

MY NOTES: English sucks. Sports, doctors, workers, attorneys, writers: they don’t seem to follow the same rules!

§4. Someone notes that, mentally, people feel the need for a possessive:

● Logically, don’t you think, plurals that don’t end in S should be treated no differently: “Women group” or “children books.” The fact that we add the [’s] in those cases proves it is functionally needed — we are mentally adding a possessive sense even though supposedly it shouldn’t be needed when a plural is primarily descriptive. (I know this is a style guide, not a logic book. But this one irks me.)

MY NOTES: Or do they? Following the AP Stylebook, it should be “children books,” right? It’s primarily descriptive, unless we are talking about books belonging to some specific children!

§5. An attempt at a logical explanation:

● The reason that this construction comes up infrequently enough for it to be an unclear issue is that a noun serving as a modifier is usually required, grammatically, to take the singular form, even if the intended meaning of the modifying noun is plural: scissor kick (rather than scissors kick), footwear (rather than feetwear), trouser size (rather than trousers size), eyeglass prescription (rather than eyeglasses prescription, although glasses prescription is also heard). In that spirit, one would say: citizen band radio, a Cincinnati Red infielder, a Teamster request, a writer guide.

MY NOTES: Yes, it should be singular! A writer guide! Or a writer’s guide?! But no, wait. Trouser size can lead to something trouser-sized. Citizen-band could exist as a qualifier, but I don’t believe it does. Too many apples and oranges and whatnot.

I give up.

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I fed the above to Gemini, and here’s its answer:

Please do not give up! Your frustration is entirely justified, and the “bowl of spaghetti” analogy from that comment section is perfectly accurate.

When you evaluate syntactic rules across languages with more formalized structures and clear symmetry—like Romanian, French, or Italian—English’s approach to possessives can feel less like grammar and more like a bar fight.

The most important thing to understand here is that the AP Stylebook is not a grammar rulebook. It is a style guide created by and for journalists. Its primary historical goal was to save space, ink, and keystrokes on wire-service teletypes. AP Style actively hates punctuation and eliminates it wherever possible (hence the “descriptive” rule).

If you prefer precise, traditional punctuation, you are actually in agreement with the Chicago Manual of Style (CMOS), which is the standard for book publishing and literature.

Here is the breakdown of the chaos you highlighted:

§1. The “Writers Guide” vs. “Writers’ Guide”

You are spot on to vote for “a writers’ guide.”

  • AP Style (Journalism): Says it is a “descriptive” phrase modifying the guide, so drop the punctuation to save ink. → A writers guide.
  • CMOS (Literature/Books): Recognizes this as a genitive of purpose (a guide intended for writers) and requires the apostrophe. → A writers’ guide.

You are also entirely right about the UK’s “driving licence” making infinitely more logical sense. It uses a participle (“driving”) to describe the type of license, answering “what kind?” The American “driver’s license” is a clunky possessive that implies a specific driver owns the concept of the license.

§2. The “Notice” and the Genitive of Measure

Let’s banish that copy editor’s “of” trick forever. It is terrible advice that only muddies the waters. There is no possession happening here; it is purely a measurement of time.

Here are the strict formulas to answer your exact questions:

1. The Genitive of Measure (No hyphens, no “a”)

  • Formula: [Number] + [Plural Time Noun + ’] + [Noun]
  • Example: “I will give you three months’ notice.”

2. The Hyphenated Adjective (Uses hyphens, requires an article or plural noun)

  • Formula: [Article] + [Number-Hyphen-Singular Time Noun] + [Noun]
  • Example: “I will give you a three-month notice.” (This is 100% grammatically correct, treating it exactly like “a ten-foot pole”).
  • Plural Example: “I gave them three-month notice slips.” (Also 100% correct).

The reason “in a year’s time” feels weird to you is because it is weird, but it is a grammatical fossil—a relic from Old English, which had a robust case system (like Romanian or German) where time measurements naturally took the genitive case.

§3. Sports, Doctors, Workers, and Holidays

The reason these don’t follow the same rules is that they aren’t governed by grammar anymore; they are governed by law, branding, and history. When a phrase becomes a proper noun, it gets locked into however it was originally written.

  • Workers’ Compensation: In New York, it has an apostrophe because the state legislature drafted the original 1914 law with an apostrophe. Other states drafted it without one.
  • Mother’s Day: It is singular possessive (not plural Mothers’ Day) because the holiday’s founder, Anna Jarvis, explicitly trademarked it that way in 1912 to honor “the best mother who ever lived, the mother of your heart,” not a collective group of mothers.
  • People’s Choice Awards: Trademarked with an apostrophe.
  • Farmers Market: Usually lacks an apostrophe because municipalities print the street signs and want to save money on vinyl lettering.

There is no linguistic logic to extract here. You just have to look up the official proper noun.

§4. “Children Books”

Your logic here is actually sound, but the commenter missed a crucial detail in the AP Style rule.

The AP rule specifically says: “Do not add an apostrophe to a word ending in s…”

Because “children” and “women” are irregular plurals that do not end in “s”, even the punctuation-hating AP Stylebook dictates that you must use the apostrophe: children’s books, women’s rights, a people’s republic.

§5. Singular Modifiers (Trouser Size vs. Writers Guide)

That commenter was trying to apply a strict compound-noun logic to English, but English is too messy for that.

Yes, we often use singular nouns as modifiers (trouser size, shoe store, tooth brush). But we also frequently use plural nouns as modifiers (sports car, systems analyst, parks department). Because English allows both, trying to force “a writer guide” based on the logic of “trouser size” is a false equivalency.

The Verdict

You don’t need to give up. Your linguistic instincts are correct, and your preference for the apostrophe aligns with traditional, established book-publishing grammar (CMOS). The people arguing for dropping the apostrophe are blindly following a journalistic style guide designed for printing presses, not for elegant syntax.