ASK DOCTOR DOROTHY PASTENSE FULLSTOP

 

What is the correct way of presenting the 24-hour clock in writing? I’ve seen 1300, 13.00, and 13:00. Also, should I leave a space between the time and am/pm, that is, should it be 12.00pm or 12.00 pm?

 

When using the 24 hour clock, there are two ways. 13:00 (with the colon) is correct when displaying a single time. Indeed, the colon is used when giving a more precise time when expressing minutes and seconds: 12:05:39 (five minutes past twelve and thirty-nine seconds, the precise time I just happened to complete writing that time). But when displaying timetable information where there is likely to be a (possibly long) list of times that public transport leave a particular point to go to its destination, it is visually clearer to drop the colon.

 

As regards the 12.00pm (no space) and 12.00 pm (with a space) issue, a look at the British National Corpus for written examples suggests that most people drop the space. The BBC news website does the same, whilst a search on Oxford University’s website presents a mix of the two styles, but most tend to drop the space. A visit to the usa.gov website has every example dropping the space.

 

So in conclusion: it is up to you, but most natives do not bother with the space.