Past Simple and Past Perfect

A. Time expressions that refer to the present, such as this morning/week/month and today, can be used with either past simple or present perfect verbs. If we think of this morning (etc.) as a past, completed time period, then we use the past simple; if we think of this morning (etc.) as a time period which includes the present moment, then we use the present perfect.

Compare:

1. I didn't shave this morning.=( the morning is over and I didn't shave)
2. I haven't shaved this morning.=( it is still the morning and I might shave later)

B. In news reports, you will often read about or hear recent events introduced with the present perfect, and then the past simple or other past tenses are used to give details:

1. The film star Jim Cooper has died of cancer. He was 68 and lived in Texas.
2. The US space shuttle Atlantis has returned safely to Earth. It landed in Florida this morning.

C. In a sentence which includes a time clause with since, we generally prefer a past simple verb in the time clause and a present perfect verb in the main clause. The time clause refers to a particular point in the past:

1.  Since Mr Hassan became president, both taxes and unemployment have increased. (rather than... has become...)
2. She hasn't been able to play tennis since she broke her arm. (rather than . . has broken..)

Notice, however, that we use the present perfect in the time clause if the two situations described in the main clause and time clause extend until the present:Have you met any of your neighbours since you've lived here? (not ...you lived...)

D. After the pattern It/This/That is/will be the first time... we generally use the present perfect in the next clause:

1. That's the first time I've seen Jan look embarrassed. (reporting a past event)
2. It won't be the first time she has voted against the government in her long career. (talking about a future event)

E. With time clauses introduced by after, when, until, as soon as, once, by the time and the time expressions, the minute/second/moment, the past simple refers to past, completed events, and the present perfect refers to future events.

Compare these examples:

1. After she left the hospital (past), she had a long holiday.
2. After Dominic has left school (future), he will be spending six months in India.
3. The minute I got the news about Sue (past) I telephoned my parents.
4. I'll contact you the minute I've got my exam results. (future)
   

Try this exercise to test your grammar.

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