Using Apostrophes in Time Expressions (Temporal Expressions)
 
Apostrophes are used in time expressions. For example:

  • 1 year's insurance
  • 2 days' leave
  • a week's pay
When it is one measure of time, the apostrophe goes before the s (e.g., one day's pay). When it is more than one measure of time, it goes after the s (e.g., two days' pay).
 

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Apostrophes in Time Expressions (Temporal Expressions)

Apostrophes are used in time expressions (e.g., three years' experience, two days' pay, one day's time). These are also known as temporal expressions.

In a temporal expression, the apostrophe is positioned before the s for single units of time and after for multiple units of time. For example:

  • I never did a day's work in my life. It was all fun. (Thomas A. Edison)
  • (As this is one day, the apostrophe goes before the s.)

  • Alan was given two days' notice.
  • (As this is two days, the apostrophe goes after the s.)

  • That is the equivalent of one year's pay.
  • (As this is one year, the apostrophe goes before the s.)

  • My car came with three year's free insurance.
  • (As this is three years, the apostrophe should go after the s.)

These are both correct.
(newspaper clipping)


This is wrong. It should be 3 months' mobile insurance.
(newspaper clipping)


This is wrong. It should be 4 years' free credit.
(newspaper clipping)
 
 
 
DO NOT USE APOSTROPHES FOR ALL TIME EXPRESSIONS – ONLY WHEN THEY COULD REPLACE THE WORD OF

The following do not have any apostrophes in them:

  • I lived in Africa for 3 years.
  • She has six months left to run on her
    loan.
This point causes confusion amongst many. As a rule, you should only use an apostrophe in an expression where the word of might have been used. For example:

  • six months' insurance
  • (six months of insurance)
  • a day's leave
  • (a day of leave)
  • She has six months' left to run on her loan.
  • (She has six months of left to run on her loan.)
    (This is nonsense. It's wrong.)
  • She has six months left to run on her loan.
  • (This is correct with no apostrophe.)
 
 
IT'S NOT ALL ABOUT TIME 

The vast majority of these expressions are time expressions, but some relate to value and distance too:

  • 10 pounds' worth of potatoes and 1 pound's worth of onions
  • a stone's throw away
 


See also:

Using apostrophes
The apostrophe error with plurals
Apostrophes replace letters
Apostrophes to show the plural of abbreviations
Apostrophes show possession