What each tense actually does

The past simple talks about a finished action at a finished time. The moment is over, done, closed. The present perfect connects a past action to now — either because the time period isn't finished, because the result still matters, or because we don't say (or care) exactly when it happened.

One way to feel the difference: past simple puts a pin on the timeline ("Tuesday," "last year," "when I was ten"). Present perfect leaves the pin out.

✅ I have lost my keys. (I still can't find them — the situation is present.) ✅ I lost my keys yesterday. (Finished event, finished time.)

❌ I have lost my keys yesterday.

That last sentence is the single most common mistake at this level, and it's worth understanding why it's wrong. The word yesterday nails the action to a closed point in time, so the present perfect — which deliberately avoids naming a closed time — can't be used with it. The same clash happens with last week, in 2019, ago, when I was a child, and any other expression that seals the time shut.

Choosing the right tense — the real triggers

Ask yourself two questions:

1. Is there a specific finished time? → Past simple.
2. Does the action matter because of its effect right now, or is the time left open? → Present perfect.

Compare:

✅ She went to Japan in 2018. (Specific year — closed time.) ✅ She has been to Japan. (At some point in her life, up to now — no time given.)

Both sentences are correct, but they do different jobs. The first tells a story about 2018. The second answers the question "Does she have the experience?"

Notice the word been. English uses "has/have been to" for life experience, not "has gone to" (which means she's there right now and hasn't come back).

Time words that lock you into one tense

Some words almost always force the choice:

• Past simple: yesterday, last month, ago, in 1999, when I was young
• Present perfect: ever, never, already, yet, just, so far, recently, since, for (with a duration up to now)

✅ Have you ever tried sushi? ❌ Did you ever try sushi? (In most standard British English this sounds wrong; American English is more tolerant of it, but at B1–B2 level, stick with the present perfect for ever/never questions about life experience.)

✅ I haven't finished yet. ❌ I didn't finish yet. (Same issue — yet points to "up to now," so it pairs with the present perfect.)

The mistake that keeps coming back

B1–B2 learners often use the present perfect to narrate a sequence of past events, especially when translating from languages where a similar-looking tense is used that way.

❌ Last Saturday I have woken up early, have eaten breakfast, and have gone to the market. ✅ Last Saturday I woke up early, ate breakfast, and went to the market.

The moment you set the scene with a finished time (last Saturday), every verb in that story should normally be past simple. The present perfect would only reappear if you suddenly shift focus back to the present:

I went to that market last Saturday, and I**'ve bought** from them three times since then.

Here the first clause is past simple (last Saturday — closed), and the second is present perfect (since then — a period reaching up to now).

Keep this principle in your pocket: finished time → past simple; open time or no time → present perfect. It won't cover every edge case in English, but it will keep you right in the vast majority of sentences you'll meet at this level.