Use periods in expressions of time.
Example:
10:00 p.m. (not PM or pm)
Time ranges use an en dash with a space on each side.
8:30 a.m. – 9:45 a.m.
RMA follows the AP style when presenting time zones. When spelled out, designations of time zones begin with capitals: Eastern Time (ET); Central Time (CT); Mountain Time (MT); Pacific Time (PT); Greenwich Mean Time (GMT). Time zone abbreviations use all capitals.