4 months' time / 4 months time

Hi

(a) is correct.

Dear Yoong Liat,

Thanks for your answer. If possible, could you please explain the grammatical point that leads you to believe a) is correct?

I have seen b) used. A 'Google' search using the format site:*.edu "3 months time"

shows many hits. Below is an example among many ( from web.mit.edu/career/www/preprof/retakemcat.pdf )
"?Individuals

There are many examples of poor grammar, punctuation and vocabulary on the internet, so you must be wary when using Google to find answers.

The possessive form (3 months' time) is the correct practice. 'The time' = 3 months; it is 3 months' worth of time, or the time 'belonging to' 3 months.

What Mister Micawber said about Google is true. It doesn't matter how ridiculous or unlikely the misspelling or grammatical mistake, you will find it in Google. For example if you look for ‘unviersity' instead of the correct spelling 'university' you will find many hits.

A

4 months time