time of day

Note: A similar topic is discussed in the article heure (écriture de l’heure) (in French only).

On this page

• Abbrevations “a.m.” and “p.m.”
• Time of day
• The 24-hour system
• Spans of time
• Additional information

Abbreviations “a.m.” and “p.m.”

The abbreviation a.m. stands for ante meridiem, which is Latin for “before midday.” The abbreviation p.m. stands for post meridiem, which is Latin for “after midday.”

Use these abbreviations with numerals only:

• 9:00 a.m. [not ninen i n e a.m.]
• 2:00 p.m. [not twot w o p.m.]

These abbreviations are usually written in lower case, with periods and with no internal spacing.

• The Prime Minister’s speech will be broadcast at 8:05 p.m.lower case p lower case 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.

• HeadlineHeadline in all caps: ECLIPSE AT 11:15 A.M. TODAY

Time of day

Except in descriptive text, write the exact time of day in numerical form. Place a non-breaking space between the time and the abbreviation a.m. or p.m.:

• Does the bus arrive at 7 p.m. or 8 p.m.?
• Louis is picking me up at 11:25 a.m.

In approximate expressions of time and in descriptive text, write out whole, half and quarter hours in words, omitting the abbreviations a.m. and p.m.:

• Drop by around six-thirty for dinner.
• We arrived shortly after quarter past seven in the evening.
• Time passed excruciatingly slowly—one o’clock, two o’clock, three o’clock …

When writing out the time of day in words, use a hyphen between the hour and the minutes, unless the minutes themselves are hyphenated:

• I leave for work between eight and eight-thirtyeight hyphen thirty.
• Megan usually leaves for work at about eight forty-fiveforty hyphen five.

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].

The 24-hour system

The 24-hour system is used in specialized fields (such as the military) and in French Canada; it’s also the most commonly used system internationally.

Therefore, in documents presented in both official languages, and in international communications, you many want to use the 24-hour system for representing time of day, in accordance with International Standard ISO 8601 and the Treasury Board Federal Identity Program Manual.

In this system, the abbreviations a.m. and p.m. aren’t used. The hour is represented by a two-digit number ranging from 00 to 23 (or 24), while the minutes are represented by a two-digit number ranging from 00 to 59. The colon is used as a separator between hours and minutes:

• 00:15zero zero fifteen (12:15 a.m., i.e. 15 minutes after midnight)
• 08:00zero eight hundred (8:00 a.m.)
• 12:00twelve hundred (noon)
• 15:39fifteen hundred thirty-nine (3:39 p.m.)
• 24:00twenty-four hundred (midnight)

Seconds may also be represented by a two-digit number ranging from 00 to 59, with a colon between minutes and seconds:

• 14:12:2614 colon 12 colon 26 (12 minutes and 26 seconds after 2:00 p.m.)

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

Converting time to the 24-hour system

12-hour system	24-hour system
12:00 p.m. / noon	12:0012 hundred hours
1:00 p.m.	13:0013 hundred hours
2:00 p.m.	14:0014 hundred hours
3:00 p.m.	15:0015 hundred hours
4:00 p.m.	16:0016 hundred hours
5:00 p.m.	17:0017 hundred hours
6:00 p.m.	18:0018 hundred hours
7:00 p.m.	19:0019 hundred hours
8:00 p.m.	20:0020 hundred hours
9:00 p.m.	21:0021 hundred hours
10:00 p.m.	22:0022 hundred hours
11:00 p.m.	23:0023 hundred hours
12:00 a.m./ midnight	00:00 (or 24:00)0 hundred hours or 24 hundred hours

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 12 a.m., use 00:00zero hundred hours (or 24:0024 hundred hours), or midnight.
• For 12 p.m., use 12:0012 hundred hours or noon.

Spans of time

Use an en dash (–) to link two figures that represent a continuous time frame. Don’t 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.]

Don’t use the en dash if the time frame is preceded by the prepositions from or between:

• He was absent from 9 a.m. to 10 a.m. [not from 9 a.m.–10 a.m.]

From must be followed by to, and between by and:

• Lunch is served between 11:30 a.m. and 2:00 p.m. [not between 11:30 a.m. to 2:00 p.m.]

In informal writing, the first a.m. or p.m. is sometimes omitted when the time span occurs in the same portion of the day (morning or afternoon). However, in formal writing, you need to repeat the abbreviation:

• The office is closed from 1 p.m. to 2 p.m. [not from 1 to 2 p.m.]

Additional information

• Heure (écriture de l’heure) (in French only)
• Elapsed time
• Daylight saving time, daylight time, standard time, summer time

Quiz

• Do you have the right time?