Definite time in the past
We use the past simple to refer to definite time in the past (when we specify the time or how long) and usually with past time expressions such as yesterday, two weeks ago, last year, in 1995:
We met in January 1975. We went to America together in 1978.
Not: We have met in January 1975. We have gone to America together in 1978.
Time up to now
We use the present perfect to talk about time up to now, that is, events that took place in the past but which connect with the present. The present perfect is often used with time expressions which indicate time up to now, for example today, this year, in the last six months:
I haven’t seen her since January 1995.
Not: I didn’t see her since January 1995.
| The last time I saw her was over 20 years ago. |
| I saw her last week but the last time I saw her before last week was over 20 years ago. |


