Grammar Tip – a.m. and p.m.

BizWritingTip reader: “I noticed in your last tip that you used a.m. instead of AM. Was there a reason for this?”

BizWritingTip response: According to both the Oxford Canadian Dictionary and The Canadian Press Stylebook, the designations for morning and afternoon are written in the lowercase with periods between each letter.


10 a.m.

3:15 p.m.

Note: There is a space between the number and the abbreviation.

In some print documents, you can use small capitals (small caps) – A.M. and P.M. – if you have that option. However, avoid the use of all-capital letters.


10 A.M. (incorrect — large caps)

10 A.M. (correct – small caps)

3:15 P.M. (incorrect – large caps)

3:15 P.M. (correct —small caps)

Don’t use AM. This is the abbreviation for “amplitude modulation.” Its most common use is with radio stations.

I trust this BizWritingTip provides you with timely information.