Each week proofreader Hannah Jones discusses and offers a remedy to common problems we encounter when writing. Today she demonstrates the use of apostrophes with time periods.

A common stumbling block for many writers is whether to use an apostrophe in phrases such as five years time/five year's time. Which is the correct usage?

An apostrophe should be used in phrases where a time period modifies a noun (e.g. notice):

two weeks' notice

a month's holiday

five years' time