Posted by: Jack Henry | January 24, 2017

Editor’s Corner: Time of Day and Time Zones

Here are the guidelines for the time of day and time zones from the JHA Style Guide for Technical Communication and Training.

Guideline Example
For time of day, use hours and minutes (8:00, not 8).

Use a.m. and p.m. (lowercase, with periods).

Use two-letter abbreviations for time zones, or spell out the time zone using capital letters. Do not indicate Standard or Daylight time.

§ ET—Eastern Time

§ CT—Central Time

§ MT—Mountain Time

§ PT—Pacific Time


§ 8:00 a.m.

§ 5:30 p.m. ET

§ 3:45 p.m. Central Time


§ 8 AM

§ 5:30 p.m. EST

§ 3:45 P.M. Central Standard Time

If you are using 24-hour time, always include a colon in the time notation. Note the time zone if necessary.

For 24-hour time, use noon and midnight when possible to avoid confusion. If it is not possible to use noon and midnight, use 12:00 to indicate noon and use 00:00 (in most cases) to indicate midnight. See exceptions for ranges below.

Use 0:00 to indicate midnight in a range of time that begins at midnight. Use 24:00 to indicate midnight in a range of time that ends at midnight.


§ The shift runs from 18:00 to 24:00 PT.

§ The shift runs from 00:00 to 06:00.

§ Lunch will be served at noon.

§ The new law will take effect at 00.00.


§ The shift runs from 1800 to 2400 PT.

§ The shift runs from 18:00 to 00:00.

§ The new law will take effect at 24:00.

Jackie Solano | Technical Editor | Symitar®

8985 Balboa Ave. | San Diego, CA 92123 | Ph. 619.542.6711 | Extension: 766711

Symitar Documentation Services

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