One of the most frequently asked questions I get, particularly from fiction writers, is whether or not to write out expressions of time instead of using numerals. The answer’s pretty typical of editorial answers to anything: sometimes, except when you shouldn’t.
Let me clarify.
Numerals or Not?
In AP style, numeral-based time is preferred over writing out the words in long form. But in Chicago style?which covers most fiction writing?the preference is to write out the time if It’s in a quarter-hour increment. So instead of writing “1:00,” you’d say “one o?clock.” “10:30” would be “half past ten” or “ten thirty,” and “4:45” would be “a quarter to five” or “a quarter of five” (the a is optional).
Example A (Chicago style): I told him I’d be finished by a quarter after three.
Example B (AP style): I told him I’d be finished by 3:15.
Example C (both Chicago and AP styles): I actually finished at 3:14.
Example D (Chicago style): I start work at nine o?clock in the morning.
Example E (AP style): I start work at 9 a.m. Note that AP style leaves off the 00 part of the time if It’s right on the hour.
There’s one distinct exception to this Chicago rule, though: when You’re emphasizing a particular time (the idea of “sharp”?that time and no other), use numerals even when It’s in a quarter-hour increment.
Example F (both Chicago and AP styles): The flight leaves at 6:15 a.m.
Example G (both Chicago and AP styles): My boss said I’d better not miss the 9:30 meeting.
On the Twelves
Regardless of which style guide You’re using, always use noon and midnight instead of 12 (or 12:00) a.m. and 12 (or 12:00) p.m. Because there’s possibility for confusion, the preference is now to drop the numbers entirely and use the words?even if You’re using numerals elsewhere in the sentence.
Example H (AP style): The party will take place from noon until 2:30.
Example I (Chicago style): The party will take place from noon until half past two (or two thirty).
Example J (Chicago and AP styles): The party will take place from noon until 2:20.
Mix and Match
If you are writing out your numbers instead of using numerals, avoid mixing the long-form numbers with abbreviations like a.m. An exception, of course, exists when You’re using noon or midnight (see above). The examples below are all in Chicago style.
Incorrect Example K: I’ll come over to your house around one thirty p.m.
Corrected Example K: I’ll come over to your house around one thirty in the afternoon.
Corrected Example K (assuming It’s obvious you mean afternoon): I’ll come over to your house around one thirty (or half past one).
Example L: If You’re not here by 1:30 p.m., we’re starting without you. Here, when I switched to numerals to emphasize the exact time, I changed “in the afternoon” to the abbreviation p.m.
Expressions like “ten thirty” are usually not hyphenated. There is an exception, though, when the time expression is used to modify, or describe a noun.
Example M: The flight will leave around six thirty.
Example N: He’s taking the six-thirty flight.
But don’t hyphenate if You’re using numerals, o?clock, a.m., or p.m.:
Example O: He’s taking the 6:30 p.m. flight.
Example P: He’s taking the six o?clock flight.
But what if you are using numerals instead of writing out the numbers? Next week we’ll cover a bit more on time punctuation (including punctuation of the 24-hour clock) and working with time zones. The following week, we’ll wrap up this timely series with everything you ever wanted to know about a.m. and p.m.
Christina M. Frey is a book editor, literary coach, and lover of great writing. For more tips and techniques for your toolbox, follow her on Twitter (@turntopage2) or visit her blog.