APPENDIX 12: TELLING THE TIME
For ordinary speaking, use clock-face time. Say the minutes first.
ten past six
a quarter past six
half past six
twenty-five to seven
a quarter to seven
We say a quarter (with or without a), but half (without a):
It's quarter to eight or It's a quarter to eight.
It's half past ten.
We say o'clock only for the exact hour: It's six o'clock.
For talking about timetables and exact arrangements, we often use digital time. Say the hour before the minutes.
We use the 24-hour clock for written timetables.
: 24-hour clock : Digital time : Clock-face time
 9:00 a.m.
 9:15 a.m.
 2:20 a.m.
 9:55 a.m.
nine a.m. =  nine o'clock in the morning
nine fifteen a.m. =  a quarter past nine in the morning
two twenty p.m. =  twenty past two in the afternoon
nine fifty-five p.m. =  five to ten in the evening
noon = twelve o'clock exactly in the day
a.m. = twelve midnight to twelve noon
midnight = twelve o'clock exactly at night
p.m. = twelve noon to twelve midnight
midday = the hours in the middle of the day