a.m., p.m.

The abbreviations a.m. and p.m. stand for the Latin ante meridiem and post meridiem, meaning before and after midday. These abbreviations should be used only with numerals (e.g. 9:00 a.m. or 9 a.m., not nine a.m.).

In Canada, these abbreviations are usually written in lower case, with periods and with no internal spacing. A non-breaking space should be used between the time and the abbreviation a.m. or p.m.

• The Prime Minister’s speech will be broadcast at 8:05 p.m. on all stations.

Regular capitals (A.M., P.M.) or small capitals (A.M., P.M.) are acceptable alternatives in headlines, lists or tables written in upper case.

• Headline: ECLIPSE AT 11:15 A.M. TODAY

Never use a.m. or p.m. with the expression o’clock or with the words morning, afternoon, evening or night.

• Sarah doesn’t answer the phone after ten o’clock (not ten p.m. o’clock).
• The lecture began at 4:30 p.m. (or 4:30 in the afternoon, but not 4:30 p.m. in the afternoon).

If the 24-hour clock is used, a.m. and p.m. are unnecessary and incorrect.

• The next flight to Thunder Bay leaves at 14:45 (or 2:45 p.m., not 14:45 p.m.).

For more information on how to write the time of day, see TIME OF DAY, ELAPSED TIME.

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