I know the difference in general, but it still confuses me when it comes to certain contexts, including the following:

I love a girl and I'm wondering if she knows that I love her. I'm talking about now here. Should I ask

Does she know that I love her?


Did she know that I loved her?

It seems to me that the latter refers to the past event

  • 1
    In this context, I would use "Does she know that I love her?" – Justin Mar 2 at 4:57
  • Justin// That said, "Do you know that I love you?" doesn't make sense, does it? because there's no point of asking when you gave the answer while asking? – Choe Guevara Mar 2 at 5:26
  • I mean in a situation where the listener is present, which is different from the example above where she is not present – Choe Guevara Mar 2 at 5:36
  • Of course it makes sense, but only if you think it possible that she already knows (or suspects) that you love her. – Kate Bunting Mar 2 at 9:01

At Quora, Richard Lueger, former editor, ESL teacher gives a reasonably comprehensive answer to the question of when to use “Do you know ...?” and when to use “Did you know ...?” [reformatted]:

Both are correct but they will usually be used in different situations....

For example, “Did you know” is commonly used [often with a that-clause] either

  • to remind someone [/ make someone aware] of something, eg “Did you know that you have to pay this bill before the end of the month?

["Did you know we're being inspected next week?"]


  • to present some interesting fact, eg “Did you know that the Nobel Peace Prize is always awarded in Oslo, Norway?

Of course, there are other possibilities, such as to ask for information about the past, eg “Did you know Marmaduke McGillicuddy when you were at school?

As for “Do you know,” it’s usually used just to ask for information, eg “Do you know when the next solar eclipse will be?” / “Do you know who ate all the cookies?” / “Do you know Marmaduke McGillicuddy?” [/ “Do you know the thirteen-times table?”]

Sometimes either can be used in a rhetorical question, where the intent is to give someone a message, not to get an answer, eg “Do/did you know you’re really stupid?” and “Do/did you know that I’ve always loved you?”

I'd just add that there is also a pragmatic difference when both options are available. "Did you know that I love you?" is ... I'll say more 'guarded', tentative perhaps, than "Do you know that I love you?" And I don't think this is reasonably considered a rhetorical question!

And "Did you know that you left the keys in the ignition?" is less likely to provoke an altercation than "Do you know that you left the keys in the ignition?" (and certainly less likely than "Do you know that you left the keys in the ignition!"

  • I really appreciate it – Choe Guevara Mar 2 at 17:26
  • Deserves at least an upvote. – Mari-Lou A Mar 3 at 10:51
  • I just did. I didn't know how – Choe Guevara Mar 10 at 10:02
  • These untrustworthy electronic voting systems :( – Edwin Ashworth Mar 10 at 12:00

If you want to ask whether somebody knows something then you could say:

Do you know that girl's name?


Do you know what time it is?

However if you are informing the person of something in the same breath it makes sense to say:

Did you know her name is Helen?

This is doing two things. It is informing the person that the girl's name is Helen, and asking whether they knew already. They know now, definitely, because you have just told them. But did they know already? That is the question.

In asking a girl

Did you know I love you?

you are telling her that you love her. She knows now. You are asking her whether she already knew, and it puts the onus on her to reply, perhaps on the lines of

I hoped so, because I love you.

  • But doesn't 'Do you know I love you?' work as well? Can you pinpoint the difference in usage? – Edwin Ashworth Mar 2 at 11:38
  • @EdwinAshworth To me "Do you know I love you?" is something to say to one's wife for example. You aren't informing her of anything, you are asking if she really and fully accepts the fact. Her perception will not change as a result of the question, so present tense is appropriate. When you say "did you know" you are conveying something which might come as a surprise. It is certainly possibile that her perception after the question will differ from before it, and so the past tense seems appropriate. – davidlol Mar 2 at 11:48
  • @davidlol&Edwin Ashworth...Thank you gentlemen for reading my post through and taking the time to respond. It was way more useful than I expected. I have pretty much to learn from this interesting and insightful dialogue of yours – Choe Guevara Mar 2 at 18:13

You are correct, "Did" is past tense indeed. While "Does" derives from "Do", which is the present tense version of the same word.

present tense: I do, She does, He does, We do, They do, It does.

past tense: I did, She did, He did, We did, They did, It did.

  • The ambiguity seems to arise because "Did you know~" is idiomatic and common among most native English speakers when asking about the current situation – Choe Guevara Mar 2 at 5:56
  • 1
    @ChoeGuevara "Do you know?" is also idiomatic when talking about the present time, particularly when talking about immediately useful information. For example "Do you know that the 8:40 train has been cancelled?". "Did you know?" is used, in my experience, for interesting rather than immediately useful information such as "Did you know that this station was built by Brunel as part of the Great Western Railway? That's why the platforms are so far apart because it was designed for broad gauge lines." You notice that I am using 'interesting' in one of its more generous definitions. – BoldBen Mar 2 at 6:37
  • Explains it I guess, I'm a non native speaker. These kind of things I'm pretty sure were "drilled" over and over back in middle school. But the way it's spoken in native countries can differ from place to place. – PassingTime Mar 2 at 6:38

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