It’s a very tricky thing trying to position yourself as a ‘writing expert’. You open yourself up to internet excoriation. Invariably, there will be errors that slip into some things (most things?) that you write, and other writing geeks will be keen to take aim at any error, perceived or actual.

Grammar Girl, in her post on comma use with strings of adjectives, uses as her first example of a string of adjectives:

When you use a string of adjectives, you often separate the adjectives with commas, as in ‘He is tall, dark, and handsome.’

But that example was always going to be separated by commas, because they were after the noun being modified, and were just, you know, a list.

You could find grammatical errors or stylistic inconsistencies in the writing of even the most authoritative people, like David Crystal or Steven Pinker; no one is immune.

English is messed up. It’s not like maths, were we can  expect a repeatable answer, every time. No matter what you do, someone will take exception. Certain rules (like comma placement, in some cases!) are more fluid. Some things are a matter of house style, like whether you use single or double quotes, or whether you spell out numbers 1–10 or use numerals.

Or whether you use an apostrophe with expressions using time, like:

He has 5 years experience.

Now the convention, traditionally, is to write it like this:

He has 5 years’ experience.

There are many writing experts out there telling us that, absolutely, there needs to be an apostrophe after the s. They might use terms like ‘genitive case’ and ‘Latin’. They generally accept that this may feel strange to some people, and, in that case, we should add an ‘of’ between ‘years’ and ‘experience’.

However, while you will see this rule followed with terms like ‘experience’ or ‘jail’, it’s not generally applied in a lot of other situations, where, if we want to be all prescriptivist about it, it should.

If we look at the grammatical form, we have:

5 years’ experience
Number > unit of measurement > noun

Let’s look at some other similar constructions. Would you add the apostrophe here?

  • 2 litres capacity
    • or abbreviated, 2000cc capacity
  • 24 months interest free
    [implied: finance].

It seems very odd to me to add an apostrophe to these, as the number and unit of measurement directly quantify the following noun. Kind of like how in the example below, the number and unit of measurement directly quantify the adjective.

The assignment was 2 days late.

(Note, as in the example above, if an adjective or preposition—such as ‘2 weeks in‘—follows the unit of measurement instead of a noun, an apostrophe is not used.)

Which makes applying the apostrophe to ‘years’ only if it’s followed by a noun feel quite arbitrary.

The Commonwealth Style Manual for Authors, Editors and Printers (6th Ed.) generally agrees:

It was previously conventional to use an apostrophe in expressions of time involving a plural reference, such as:

  • six weeks’ time
  • three months’ wages

The apostrophe is now often left out. Again, the sense of these phrases tends to be more descriptive than possessive.

My preference is to leave it out (still included in singular references, such as ‘a year’s time’) as there is no effect on meaning. Of course, if I’m working somewhere that uses the apostrophe in these situations as part of their house style, I can comply.

So, if it in no way affects meaning, why do some people insist it stays? Is it one of those social markers that people like to use to demonstrate their education?