A friend and I were discussing a past event and she said:

"I don't know when you left yesterday"

but I thought she ought to say:

"I don't know when you leave yesterday"

Please tell me which one is correct?

  • 1
    Your departure occurred yesterday, in the past, and calls for the past-tense form, left. I have to wonder what makes you think that the present-tense form leave would be more appropriate; if you could edit your question to include that it would help us unravel your underlying misunderstanding. ... I invite you to consider having the moderators move this question to English Language Learners; if you feel that is appropriate, click on the flag link immediately above the question tags. Jun 21, 2015 at 17:47

2 Answers 2


Pretty sure your friend's right: leave is PRESENT tense (i.e. I don't know when you leave today), whereas left is the PAST tense of leave (i.e. I don't know when you left yesterday). Hope that helps.


The phrase "I don't know what time you left yesterday." would be better than both of those phrases.

Your second phrase is completely incorrect because it mixes a present tense with a past word form.

I leave yesterday*

This sentence is incorrect, for your present form, "leave", clashes with the past form, "yesterday".

The first sentence is heading in the right direction, yet it's the word "when" that messes up the sentence. The correct form would be:

I left yesterday.

If you want to incorporate the rest of the sentence into it, the correct form would be:

I don't know (at) what time you left yesterday.

And no offense, but if you are still learning the English language, I suggest you post this on English Language Learners

  • 1
    For the sake of perfection I would suggest I don't know AT what time you left yesterday
    – WS2
    Jun 21, 2015 at 21:00
  • Should I put it in parenthesis?
    – Klyzx
    Jun 22, 2015 at 13:48
  • Oh no! I don't know at what time you left is quite idiomatic, though people do tend to shorten it by dropping the at. I prefer to keep the at.
    – WS2
    Jun 22, 2015 at 19:24
  • Changed it to incorporate the at.
    – Klyzx
    Jun 23, 2015 at 13:58

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