This use of the Present Perfect turns on one single question: Has the time period finished, or is it still going?
Think of time periods as containers. Some containers are sealed — they are closed, finished, over. Last week, last year, in 2019, yesterday, last month — these are sealed containers. Whatever happened inside them is in the past. You use the Past Simple for events inside a sealed container.
Other containers are still open — they have not finished yet. Today, this week, this month, this year, this morning, so far, up to now — these containers are still being filled. You are still inside them as you speak. Anything that has happened inside an open container is described with the Present Perfect, because the period has not ended and more can still happen.
This is the subtlest and most important point. The event itself may have happened at exactly the same clock time — but the tense changes depending on whether the surrounding period is still open.
Imagine it is Tuesday morning at 10am:
The same event. The same day. But the tense shifts the moment the period closes. This is why the Present Perfect is so tied to the present moment — it only works when the time container is still open around you.
✗ I drank three coffees today. · She called me twice this morning. · We had three meetings this week.
✓ I have drunk three coffees today. · She has called me twice this morning. · We have had three meetings this week.
The Past Simple closes the door on the event — it says the action is finished and belongs entirely to the past. But if the time period is still open, you are still inside it, and more events could still happen within it. The Present Perfect keeps that door open. Whenever you use today, this week, this month, this year, ask yourself: is the period still going? If yes — Present Perfect.
✗ She has called me twice yesterday. · We have had three meetings last week. · They have scored four goals last season.
✓ She called me twice yesterday. · We had three meetings last week. · They scored four goals last season.
The words yesterday, last week, last year, last season, in 2019 all mark a period that is completely over. The container is sealed. You cannot use the Present Perfect with a sealed container — this is one of the most absolute rules in English grammar. These words always trigger the Past Simple, without exception.
✗ (At 3pm) I have drunk three coffees this morning. (Wrong if "this morning" is over)
✓ (At 10am) I have drunk three coffees this morning. (Morning still in progress — Present Perfect)
✓ (At 3pm) I drank three coffees this morning. (Morning is now finished — Past Simple)
This morning is interesting because it depends entirely on what time it is when you speak. If it is still morning, it is an open period — use the Present Perfect. If the morning has ended (afternoon or evening), it is a closed period — use the Past Simple. The same logic applies to this evening if the evening has not yet started when you speak. Always check: am I still inside the period, or has it closed?
✗ I drunk three coffees today. · She called me three times this week. · We have drank two bottles today.
✓ I have drunk three coffees today. · She has called me three times this week. · We have drunk two bottles today.
The Present Perfect always requires both parts: the correct form of have/has AND the correct past participle. Omitting have/has entirely, or confusing the past participle with the Past Simple form (drunk not drank; written not wrote; spoken not spoke) are very common errors. Always double-check both elements.