Indicate time with numerals before “a.m.” or “p.m.” (always lowercase and always followed by periods). When writing a time that falls on the hour, state only the hour before “a.m.” or “p.m.” (Don’t use “:00.”)
In editorial content, “o’clock” is acceptable but should be avoided in most communications. Use “noon” and “midnight” instead of “12 p.m.” or “12 a.m.”
To designate a range of time, use a hyphen or en dash. Depending on design, adding a single space to each side of the hyphen or en dash can improve appearance and readability.
Right: 3 p.m., 3–5 p.m., 9 a.m. – 5 p.m.
Right: Noon–1 p.m.
Right: The concert begins at 8:30 p.m.
Wrong: 3:00 p.m.
Wrong: 3 p.m.–5 p.m.
Wrong: 12 noon, 12 p.m.
Wrong: 12 midnight, 12 a.m.
When designating a time of day along with its date and day of the week, follow this sequence: day of week, date, time of day.
Right: Wednesday, Sept. 8, at 2 p.m.