spans of time

The guidelines below show how to write spans of time in different formats.

Using an en dash

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

• Lunch: 12:00 p.m.–1:00 p.m.  
• Plenary session: 1:00 p.m.–2:30 p.m.  
• Closing: 4:00 p.m.–4:15 p.m.

Using from … to, between … and

Do not use the en dash if the sequence is introduced by the preposition from or between. From should be paired with to, while between should be paired with and. 

• The party is from 9 p.m. to 2 a.m. (not from 9 p.m.–2 a.m.)
• We will meet between 3:30 p.m. and 3:45 p.m. (not between 3:30 p.m.–3:45 p.m.)

Repeating a.m. or p.m.

In informal writing, the first a.m. or p.m. is sometimes omitted when the span of time 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.)

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