time

Use figures for time of day except for noon and midnight. Also designate with a.m. or p.m.—with periods—and do not use :00 (11 a.m.; 3:30 p.m.; 9 a.m. to 5 p.m.; 8 hours, 30 minutes, 20 seconds). See also a.m. and p.m.

Spell out numbers less than 10 standing alone and in modifiers (I’ll be there in five minutes. He scored with two seconds left. He works an eight-hour day.)

Avoid such redundancies as 10 a.m. this morning. An acceptable abbreviation for all day, every day is 24/7.