When do we use the simple past, and when do we use the present perfect?
We use the simple past to talk about things that happened in the past and were completed in a time period that is finished.
- Tom bought a new computer yesterday.
- Jan wrote her essay last week.
- They passed the TOEFL test last month.
- I went to New York last year.
- She turned in her assignment two days ago.
Notice the time expressions refer to a period of time that is completed in the past.
We use the present perfect when we talk about things that were completed in the past, but the time period is not yet finished. Such as this week, this month, this year, my life. We generally don’t use a time expression when using the present perfect because the stress is on the completed action as it relates to the present and not on the time.
- Tom has bought a new computer, so he can complete his assignment.
- Jan has written her essay, so she doesn’t have to study tonight.
- They have passed the TOEFL test, so they can begin university courses.
- I have been to New York several times, so I know the city pretty well.
- Because she has turned in her assignment, she doesn’t have to come to class today.
Present Perfect / Present Perfect Progressive
We may also use the present perfect or the present perfect progressive to talk about things that were started in the past but are not yet finished. In this case, we usually use for (a length of time) or since (a point in time).
- I have lived in New York for three years. OR I have been living in New York since I came to America.
- Akiko has studied English for one year. OR She has been studying English for one year.
- He has been traveling for three days. OR He has traveled since Monday.