12.00 — It's twelve o'clock.
6.30 — It's half past six.
4.15 — It's quarter past four.
1.45 — It's quarter to two.
8.10 — It's ten past eight.
11.50 — It's ten to twelve.
6.40 — It's twenty to seven.
3.20 — It's twelve past three.
5.25 — It's twenty-five past five.