A part of studying English personally and living in Canada that I found really confusing when speaking English was, "Should I use the past tense or the present perfect in this situation?" Since both are interpreted simply as "~ed" in Korean, I would often hesitate and stutter while trying to decide which one to use.

In Units 13 and 14, we will study the differences between these two tenses. Let's organize them together.

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1. Present Perfect (have p.p.): Connecting the Past and Present

The essence of the present perfect is a state where an event that happened in the past continues to have an effect up until the present. In other words, mathematically, it can be represented by the formula: (Past state) = (Present state).

① Checking the current status (Interrogative)

Asking someone a question using the present perfect is like borrowing a past action to ask, "So, what is the situation like right now?"

• "Are you ready to go? Have you finished your coffee?"
  • (Are you ready to go? Have you finished your coffee?)
  • ➔ This is a situation where you use the present perfect to check if the act of drinking coffee, which started in the past, has been completed at this very moment, resulting in the state of "being ready to leave."

② A present period that has not yet concluded

If the period mentioned has not yet passed at the time of speaking, use the present perfect (today, this week, since 2010, etc.).

• I've written two reports this week.
  • ➔ Since this week is not over yet, there is a possibility that more will be written.

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2. Past Tense (did): Complete Disconnection from the Present

On the other hand, the past tense is simply a point in time that has already passed. In most cases, (Past state) =/ (Present state), meaning that the event that occurred in the past is finished, and the state may be different now.

① A past point in time when an event is already finished

If an expression that points to a specific past time (yesterday, last year, ten minutes ago, etc.) is attached to the end of the sentence, use the past tense.

• Tom lost his key yesterday.
  • ➔ It only states the fact that happened yesterday. (Whether he found it or not cannot be known from this sentence, and unlike the present perfect, the connection to the present is severed.)

② Using 'When' / 'What time' to pinpoint a specific moment

If you ask, "When did that happen?", the focus of the conversation shifts from the present to a specific point in the past. Therefore, you must use the past tense in these questions.

• When did you buy this jacket?
• What time did you get up this morning?

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Summary

• The state or result right in front of you now ➔ Present perfect (have done)
• A fact that happened in the past that has already passed ➔ Past tense (did)

I have tried to organize this as simply as possible, but it might still be slightly lacking. If you have any suggestions regarding the content or if there is anything incorrect, please send me an email through the "Contact" menu! I will review and revise it.

Keep up the good work with your studies today!