English has two ways to talk about the past, and choosing between them is about where your attention is, not about how long ago something happened.
I have lost my keys. → I still cannot get in.
I lost my keys yesterday. → A finished story.
What the present perfect does
- The action happened at some point before now.
- The result or the relevance is in the present.
- You are not saying exactly when — and often you cannot.
Three jobs it does
| Job | Example |
|---|---|
| A result you can still see | She has broken her arm. |
| Experience in your life so far | I have been to Japan. |
| Something that started before and continues | We have lived here for ten years. |
If you can add a finished time — yesterday, in 2019, last week — you almost certainly want the past simple instead. We will come back to that properly on page seven.