المضارع التام

The present perfect is used when the time period has not finished:
I have seen three movies this week.
(This week has not finished yet.)

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The present perfect is often used when the time is not mentioned:
Gerry has failed his exam again.

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The present perfect is often used when the time is recent:
Ikuko has just arrived in Victoria.

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The present perfect is often used with for and since.
Greg has lived here for 20 years.
Greg has lived here since 1978.