По 12: 00 18: 15 19: 45 20: 30 15: 00 21: 30

12.00It is twelve o'clock.18.15 It is quarter past seven/ 19.45 It is quarter to eight/ 20.30 It is half past nine/ 15.00 It is three o'clock/ 21.30 It is half past ten

A twelve o' clock-12:00
A quitar past six-18:45
A quitar to eight-19:45
A half past eight-20:30
A three o' clock-15:00
A half past nine.