12:00 = midday

24:00 = midnight

Using 'a.m' and "p.m." in more formal language and usually written.

Ex: Banks are open from 9:30 a.m. to 2:30 p.m.

When time is a fraction of a minute, if less than 30 is used the adverb 'past'.

If it is higher, indicating the minutes followed by the preposition 'to'.

First Says The Minutes And after The Hour.