A present tense,NOT a future tense
is used in an adverb clause of time.
After she graduates,she will get a job.
After she (had)graduated,she got a job.
Before
A present tense,NOT a future tense
is used in an adverb clause of time.
I (had)left before he came.
I will leave before he comes.
When
WHEN =at that time
to introduce a single completed event that takes place in the middle of a longer activity or event notice the different time relationships expressed by the tenses.
When I arrived, he was talking on phone.
When I was in Chicago, I visited the museum.
While &as
While, as= during that time
To talk about two longer events happen at the same time.
While/as I was walking home, it began to rain.
While ≈ but
He gets £50,000 a year, while I get £20,000.
As ≈ because/ in the same way/although
As it was getting late, I decided to book into a hotel.
This year, as in previous year, tickets sold very quickly.
Angry as he was, he couldn't help smiling.
By the time
By the time= one event is completed before another event.
By the time he arrived, we had already left.
By the time he comes, we will have already left.
Since
Since =from that time to the present
I haven't seen him since he left this morning.
Since≈ because
Since he is here, I don't need to stay to help.
Until,till
Until /till=to that time and no longer
We stayed there until/ till we finished our work.
Not …until
We didn't leave there until we finished our work.
As soon as/once
As soon as/once = when one event happens, another event happens soon afterward.
As soon as/once it stops raining, we will leave.
As long as/ so long as
As long as/so long as = during all that time, from beginning to end.
I will never speak to him as/so long as I live.
Whenever/every time
Whenever = every time
Whenever/ every time I see her, I say hello.
The first/last/next time
The first time(that)I went to New York, Iwent to an opera.
I saw two plays the last times(that)I went to New York.
The next time(that) I go to New York, I'm going to see a ballet.