a) in the Present: Present Perfect - since - Present Perfect,
e.g.: I have been making a lot of repairs since I have been living in this flat.
She has been crying since she has been watching the movie.
In the above examples both action started in the Past and are still in course.
b) in the Past: Past Tense - when/ while - Past Tense
e.g.: The children left for school while/ when I was still sleeping.
What were you doing while she was washing up ?
I was (just) leaving when he come.
In the above combinations of Past Tenses (Simple and Continuous Aspect) the actions are both simultaneous and independent. But if we use the Past Simple for both actions, when acquires the meaning of because, and the actions in the Main Clause appears as the consequence of the action in the Secondary Clause.
e.g.: We went to see him when we heard he was in hospital.
b) in the Future: Simple Future - when - Simple Present,
e.g.: I shall change it when it doesn't work any more, not before.
She says he will move the country when he retires.
Simultaneous actions in the Future cannot be negative (negation - in either
the Main or the Secondary Clause - implies condition, which is expressed by if or nuless).
Simultaneous action in the Present (Present Tense in both Clauses) suggest FREQUENCY (when meaning of whenever, in this case).
II. ANTERIORITY
in the Past:
a) for an action that had already ended when another acton was performed,
Past Perfect Simple - before/ when - Past Tense Simple
e.g.: I had bought the book before I read the review.
The police had already caught the thief, when his accomplice
finally confessed.
Past Tense - after/ as soon as - Past Perfect Simple
e.g.: We realised where we were only after we had looked at the map
three times.
I recognized her as soon as I had heard her voice.
b) for an action that was in course when another action interrupted it,
Past Perfect Continuous - before/ when - Past Tense Simple
e.g.: He had been working on this problem for month before he
solved it.
Mr. Cook had been living in India for two years and a half when
he decided to rejoin his family.
in the Future:
a) for an action that will take place after another action is performed,
Simple Future - when/ after - Present Perfect
e.g.: You'll go out only after it has stopped raining.
She will probably find it when/ after she has tidied up.
b) for an action that will end before another actionis performed,
- Future Perfect - when/ by the time - Simple Present
e.g.: I'll have been back by the time you finished cooking.
When the clock stikes nine, I'll have been reading for four hours.
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