When the present perfect is used, it indicates a completed action in the past before now. Duration and time expressions like “for two days”, “yesterday” and “recently” are not important and not needed. What is important is that the action is done.
Completed actions in the past
- They have eaten. – [ So they are not hungry now.]
- I’ve peeled the oranges and (have) cut them for you. – [So it’s easier for you to eat it.]
- Sammy has returned the book to me. – [So I now have the book.]
Notice that there is an effect of the action. In Example #1 for instance, because “they have eaten”, the effect is “they are not hungry now”. The time they ate is not important. Use “has/have” followed by the past participle – not the simple past form – of the verb. That means, it is incorrect to say:
- I have ate.
- I ate already.
You may also add the word “already” to emphasize the action. Here are modifications to the examples above:
- They have already eaten.
- I’ve already peeled the oranges and (have) cut them for you.
- Sammy has already returned the book to me.