past perfect and simple past

Past simple and present perfect

Time expressions that refer to the present, such as this morning/ 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:

·I didn’t shave this morning. (= The morning is over and I didn’t shave)
·I haven’t shaved this morning. (= It is still the morning and I might shave later).

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.
·Since Mr Hassan became president, both taxes and unemployment have increased. (rather than.. has become…)
·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)

After the pattern It/ that/ this/ is/ will/ be the first time…. We generally use the present perfect in the next clause:

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


Notice, however, that after it/ that/this was the first time… we generally use the past perfect.
·It was the first time I’d walked to Ella outside the office.

With time clause 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:
·After she left hospital (past), she had a long holiday.
·After Dominic has left school (future), he will be spending six months in India.
·The minute I got the news about Sue (past) I telephoned my parents.
·I’ll contact you the minute I’ve got my exam results. (Future)

In the time clause in sentences like this it is possible to use the past perfect instead of the past simple (e.g. after she had left…) and the present simple instead of the present perfect (e.g. after Dominic leaves..) with the same meaning.