Use a single digit for whole hour times, full time for other increments, followed by a space and either a.m. or p.m. If a time range contains a mixture of a whole hour and a partial hour, use the full time for the whole hour.
Never use 12 a.m. or 12 p.m. Instead, for clarity, use Midnight or Noon.
The contact component automatically formats hours for offices and individuals.
9 a.m. - 4 p.m., 9:30 a.m. - 4:30 p.m., 9:00 a.m. - 4:30 p.m.