Differences of usage

A

• the present perfect simple is used when there are no references to a precise period of time (I’ve won!), when an action started in the past and still continues or has a relevance to the present (Look! I’ve changed my hairstyle) or when a period of time in which an action took place isn’t completely over (I’ve worked hard today)
• The past simple is used to talk about actions and experiences that have already been concluded. They took place in a defined moment in time and have been fully completed (for example, past summer holidays or something that happened yesterday). Compare:

The girls have been here for an hour. (They arrived an hour ago and they are still here)

They  were here an hour ago. (but now they have left)

I’ve seen this film twice! (I don’t say when I saw it)

I saw this film last Saturday. (I specify when I saw it)

Look at the difference:

I haven’t seen him this morning.

(present perfect simple because it is still morning when I say it)

I didn’t see him this morning.

(past simple because I say it in the afternoon or evening)

B

The past simple is also used:

• in questions with When, because it refers to a precise period of time.

‘When did you go to London?’ ‘I went there last summer.’

• in historical narrative, to talk about events that happened in the past or to talk about famous characters, even if the dates aren’t mentioned.

Wellington defeated Napoleon at the battle of Waterloo.

C

The present perfect simple is often used when starting to recount an event or an experience, also without specifying the exact time. When the experience is put into context and details are asked or given, the story continues in the past simple.

A: You know, I’ve won a prize in a radio competition.

(I don’t say when à present perfect simple is used)

B: Really? What did you win?

(I ask for details à past simple is used)

A: I won a collection of music CDs.

(I give details à past simple is used)

D

In American English, the past simple is used more than the present perfect simple in sentences with just, already and yet.