Time of day

Writing the time of day can be confusing. Is it 2 p.m. or 2 P.M.? Should there be periods in a.m. and p.m.? Does 12 a.m. mean midnight or noon?

Here are some guidelines to help you write the time of day.

Exact time

Write the exact time of day in numerical form. A non-breaking space should be placed between the time and a.m. or p.m. In Canada, the abbreviations a.m. and p.m. are usually written in lower case, with periods and no internal spacing:

• Does the show start at 7:30 p.m. or 8:00 p.m.?
• Louis is picking me up at 11 a.m.

In approximations and descriptive text, write out the time in words:

• Drop by at around six o'clock for dinner.
• Time passed excruciatingly slowly—one o'clock, two o'clock, three o'clock…

Spans of time

Use an en dash to link two figures that represent a continuous sequence. Do not put a space on either side of the en dash:

• Business hours: 9:00 a.m.–5:00 p.m. (or 9 a.m.–5 p.m.)

Do not use the en dash if the sequence is introduced by from or between:

• He was absent from 9 to 10 a.m.
• Lunch is served between 11:30 a.m. and 2:00 p.m.

The 24-hour system

The 24-hour system is used in specialized fields (such as the military) and in French Canada; it is also the most commonly used system internationally. In this system, the hour is represented by a two-digit number ranging from 00 to 24 (e.g. 00:01, 05:00, 13:45, 23:59). The abbreviations a.m. and p.m. are not used.

To convert time from the 12-hour to the 24-hour system, simply add 12 hours to any hour after noon:

To avoid confusion between 12 a.m. and 12 p.m., use the 24-hour system, or write out the time in words, depending on the context:

For more information on how to write the time of day, see sections 1.21, 1.22, 5.12 and 5.13 of The Canadian Style.