When to use the present perfect?
When something started in the past and is still relevant or ongoing NOW. To demonstrate, let’s think about coffee. When you drink coffee, (unless you have decaf) it has caffeine in it which stays in your system hours after drinking it. So, even if you drink the coffee in the morning you might still feel the effects hours later, in the afternoon say. Have you drunk coffee today? How many cups of coffee have you drunk?
Buuuut If you are going to use a finished time in the sentence (yesterday, last week, February, last summer, 1985, and possibly this morning [if now is past 12pm], when you were a child, or when you graduated) You NEED to use the simple past tense. Why? Because it’s going with a finished time, and in English that means it has to be finished too – it’s a grammar rule.
Sooo, did you drink any coffee yesterday? I did and I couldn’t sleep last night thanks to said coffee ZzzzzzZZZzz
Coffee is a nice example because we can see how something in the past can effect now. But this also works with other things that started in the past, such as learning English – how long have you been learning? Did you start when you were at school? Have you finished the project yet?
We also use the Perfect tense to talk about experiences. Such as travelling to different countries, trying something for the first time, watching a film or meeting a famous person.
Have you ever met someone famous – I met Chris Rock when I worked in a sunglasses shop in Manchester. I couldn’t convince him to buy any glasses though. I haven’t met anyone as famous as him since.