For a time on the hour, say It's + the number + o'clock.
o'clock = right on the hour
It's seven o'clock.
It's twelve o'clock.
The class starts at nine o'clock.
Try it: The clock shows 8:00. ___ eight o'clock. (It's / It has / There is) Answer: It's — To say the time, start with It's: It's eight o'clock. "It has" and "There is" are not how we say a time.
past = minutes after the hour
For minutes after the hour, say the minutes + past + the hour: ten past six = 6:10.
It's ten past six. (6:10)
It's five past nine. (9:05)
It's ten past three. (3:10)
Not "It's six past ten. (for 6:10)" — say "It's ten past six. (6:10)". Say the minutes first, then past, then the hour: ten past six, not six past ten.
Try it: The clock shows 4:10. It's ten ___ four. (past / to / after) Answer: past — For minutes after the hour, use past: ten past four (4:10). "To" is for minutes before the next hour; "after" is not used to tell the time this way.
to = minutes before the next hour
When it is getting close to the next hour, say the minutes + to + the next hour: ten to seven = 6:50.
It's ten to seven. (6:50)
It's five to one. (12:55)
It's ten to five. (4:50)
Not "It's ten past seven. (for 6:50)" — say "It's ten to seven. (6:50)". When the minutes are heading up to the next hour, count the minutes left: 6:50 is ten to seven, not ten past.
Try it: The clock shows 8:50. It's ten ___ nine. (to / past / before) Answer: to — 8:50 is close to nine, so count the minutes to the next hour: ten to nine. "Past" is for after the hour; "before" is not used to tell the time this way.
half past, quarter past, quarter to
Use half past for :30, quarter past for :15, and quarter to for :45. (A quarter is 15 minutes.)
It's half past two. (2:30)
It's quarter past six. (6:15)
It's quarter to nine. (8:45)
Try it: The clock shows 2:30. ___ two. (half past / quarter past / half to) Answer: half past — 2:30 is half an hour after two, so it's half past two. "Quarter past" is :15, and "half to" is not a real phrase.
Asking the time
To ask the time, say What time is it? You can also ask What's the time?
What time is it? — It's half past four.
What's the time? — It's ten to six.
Excuse me, what time is it?
Try it: You want to know the time. What do you ask? (What time is it? / How time is it? / What is time?) Answer: What time is it? — To ask the time, say What time is it? "How time is it" uses the wrong question word, and "What is time" asks about the idea of time, not the clock.
Try it: The clock shows 7:15. It's ___ seven. (quarter past / quarter to / half past) Answer: quarter past — 7:15 is fifteen minutes after seven, so it's quarter past seven. "Quarter to" is :45, and "half past" is :30.