Time
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You can show time by using either the 24-hour or 12-hour clock.
The 24-hour clock is the preferred format for international audiences and the format used in most computer systems, so use the 24-hour clock when possible.
If the technology or interface that you're documenting shows or uses the 12-hour clock, then be consistent with the interface and use the 12-hour clock.
24-hour Clock
When you use the 24-hour clock to show time, use the following guidelines:
Use a colon to separate the hours, minutes, and seconds.
Show the hours, minutes, and seconds with two digits each, even if the leading digit is 0.
If you need to show a time zone, use Coordinated Universal Time (UTC), and indicate the time-zone offset from UTC.
Examples |
|---|
08:29:37 |
18:30:59 |
18:00:00 to 20:30:00 |
10:30:00 (UTC -6) (refers to CT) |
12:00:00 (noon) |
00:00:00 (midnight) |
12-hour Clock
When you use the 12-hour clock to show time, use the following guidelines:
Use a colon to separate the hours and minutes. If the minutes are 00, you don't need to show them unless you're showing a span of time that includes a time with minutes.
Use uppercase letters for abbreviations of ante meridiem (AM) and post meridiem (PM). Separate these abbreviations from the time with a space. Do not use periods in the abbreviations.
When specifying time zones, show both the spelled-out name and the abbreviation. Show the name in lowercase letters; use uppercase letters and no periods for the abbreviation.
Avoid references to standard and daylight saving time because the appropriate designation changes frequently. However, if you need to include such a reference, insert S (for standard) or D (for daylight) as the second character in the abbreviation.
When referring to 12 AM, use 12 midnight or just midnight. When referring to 12 PM, use 12 noon or just noon.
Examples |
|---|
10:29 AM |
6 PM |
6:00 PM to 8:30 PM |
10:30 AM Central Time (CT) |
1:30 PM Central Standard Time (CST) |
midnight |