There are three different ways of saying the time:
1) In conversation, we use past ( or in American English after ) and to ( or in American English of ).

7.05 – five past seven
7.15 – quarter past seven
7.20 – twenty past seven
7.30 – half past seven
5.40 – twenty to six
5.45 – quarter to six
5.50 – ten to six
6.00 – six o’clock

2) Sometimes we use the figures only. Say the figures in the oder you see them.

5.05 – five oh five
5.15 – five fifteen
5.20 – five twenty
5.35 – five thirty-five
5.45 – five forty-five
5.50 – five fifty
5.30 – five thirty
5.55 – five fifty-five

With this form, we often say a.m. for the morning and p.m. for the afternoon and evening.

The office closes at 5.30 p.m.
Breakfast is served between 7.00 and 9.00 a.m.

3) In Britain and USA, we usually use the 24-hour clock only to talk about travel time tables.

17.20 – seventeen twenty
22.45 – twenty-two forty-five