Use the Past Simple for a finished action at a time you can name: I lost my keys on Saturday. Use the Present Perfect when the past action matters now and the time isn't the point: I have lost my keys.
Same situation, two choices. Pick an example.
I lost my keys on Saturday.
The action sits in a closed box in the past. You can say when. What happened next doesn't matter.
I have lost my keys.
The action happened before, but it reaches into now. You care about the result or experience, not the moment.
| Rule | Past Simple | Present Perfect |
|---|---|---|
| Form | I worked · Did you work? | I have worked · Have you worked? |
| Focus | When it happened | The result or experience now |
| Time words | yesterday, in 2019, two days ago, last week | just, already, yet, ever, never, since, for |
| Typical question | When did you…? | Have you ever…? · …yet? |
I _____ my homework. Can I go out now?
Paste an email or an essay. Clarigram marks the mistakes you actually make, shows the rule behind each one as a picture, and builds your practice from them.
No. Any word that names a finished time (yesterday, last year, in 2019, ago) needs the Past Simple.
It's common in spoken American English. British English, and most exams, expect "Have you eaten yet?"
For gives a length of time (for five years). Since gives the starting point (since 2020). Both usually take the Present Perfect when the situation is still true.