Collins Cobuild

Unit 96
Time clauses
Main points
You use time clauses to say when something happens.
Time clauses can refer to the past, present, or future.
Time  clauses  are  introduced  by  words  such  as  ‘after’,  ‘when’,  or
‘while’.
A  time  clause  needs  a  main  clause  to  make  a  complete  sentence.
The time clause can come before or after the main clause.
1
You use time clauses to say when something happens. The verb in the
time clause can be in a present or a past tense.
I look after the children while she goes to London.
I haven’t given him a thing to eat since he arrived.
WARNING: You never use a future tense in a time clause. You use
one of the present tenses instead.
Let me stay here till Jeannie comes to bed.
I’ll do it when I’ve finished writing this letter.
2
When you want to say that two events happen at the same time, you
use a time clause with ‘as’, ‘when’, or ‘while’.

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We arrived as they were leaving.
Sometimes the two events happen together for a period of time.
She wept bitterly as she told her story.
Sometimes one event interrupts another event.
He was having his dinner when the telephone rang.
John will arrive while we are watching the film.
Note that you often use a continuous tense for the interrupted action.
See Unit
60
.
3
When you want to say that one event happens before or after another
event,  you  use  a  time  clause  with  ‘after’,  ‘as  soon  as’,  ‘before’,  or
‘when’.
As soon as we get tickets, we’ll send them to you.
Can I see you before you go, Helen?
When he had finished reading, he looked up.
Note that you use the past perfect to indicate an event that happened
before another event in the past.
4
When you want to mention a situation which started in the past and
continued until a later time, you use a time clause with ‘since’ or ‘ever
since’. You use a past simple or a past perfect in the time clause, and a
past perfect in the main clause.
He hadn’t cried since he was a boy of ten.
Janine had been busy ever since she had heard the news.
I’d wanted to come ever since I was a child.
If the situation started in the past and still continues now, you use a
past  simple  in  the  time  clause,  and  a  present  perfect  in  the  main
clause.

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I’ve been in politics since I was at university.
Ever since you arrived you’ve been causing trouble.
Note  that  after  impersonal  ‘it’  and  a  time  expression,  if  the  main
clause is in the present tense, you use ‘since’ with a past simple.
It is two weeks now since I wrote to you.
If  the  main  clause  is  in  the  past  tense,  you  use  ‘since’  with  a  past
perfect.
It was nearly seven years since I’d seen Toby.
For ‘since’ as a preposition, See Unit
40
.
5
When you want to talk about when a situation ends, you use a time
clause with ‘till’ or ‘until’ and a present or past tense.
We’ll support them till they find work.
I stayed there talking to them until I saw Sam.
She waited until he had gone.
6
 When  you  want  to  say  that  something  happens  before  or  at  a