Per AP Style, add periods between a.m. and p.m. Use figures except for noon and midnight. A colon should be used to separate hours from minutes. Examples:
9 a.m., 5:25 p.m.
For ranges, use a hyphen or the word “to”: 8 a.m. to 5 p.m. or 8-11 a.m., noon-5 p.m. Also see abbreviations, acronyms and initialisms.
