How should I write the following sentence like a native does:

By what time did you stay up for work last night?
Until what time did you stay up for work last night?

I think both of them are incorrect.

Please note that this question has nothing to do with my previous threads. I am asking about the structure of until/by + "what time" at the beginning of the sentence.

  • If in this context, staying up is only due to the work, why create ambiguity? Simply ask - When did you sleep last night! :)... However, I'd prefer - What time you were uptil the last night, finishing work?
    – Maulik V
    Apr 15, 2014 at 2:09
  • Thanks @MaulikV, but I'm sure that's not my desirable answer, which I'm waiting for.
    – A-friend
    Apr 15, 2014 at 2:25
  • 1
    There are several variations on this depending on what exactly you mean: How late were you at work last night? (doesn't imply when they went to bed, just when they left to go home) How late were you up working last night? (does imply that they went to bed immediately after quitting for the night) What time did you get to sleep last night (context can imply they were working until they went to sleep). Did you pull an all-nighter? (Assumes they will contradict you and tell you what time they left or went to sleep)
    – Jim
    Apr 15, 2014 at 2:55
  • Thank you @Jim, for the informative comment of you, but one more question; How about if I change the sentences in the following way: (then I need to change again or not): - By what time did you work last night? - Until what time did you work last night?
    – A-friend
    Apr 15, 2014 at 3:01
  • 1
    Until what time did you work last night is grammatically correct, but not something a native is likely to say in informal conversation between friends or coworkers.
    – Jim
    Apr 15, 2014 at 3:02

2 Answers 2


There is a lot of confusion because of your example sentences, which seem to be drawing attention away from the issue you want to discuss.

Stay up is a phrasal verb that means stay awake or remain out of bed. If I say, "I stayed up until midnight last night," that essentially means "I went to bed at midnight last night," or, "I fell asleep at midnight last night."

So, the phrase stay up for work seems a little awkward. It's not something I would normally say, but I suppose I could contrive of a situation where I might say it. For example, let's say I know someone who is on call. They tell her, "You need to be ready to come into work if we call you. However, if we haven't called you by a certain time, you won't be called at all." If I don't know what that time is, and I'm curious, I could ask:

Until what time did you stay up for work last night?

meaning, what time were you able to finally go to bed?

Perhaps you meant "stay at work", which makes a lot more sense:

How late did you stay at work last night?

meaning, "What time did you finish work last night, and head home?"

If I wanted to express with one of those two dastardly prepositions (by or until), I would use until:

Until what time were you here at work last night?

Another possibility is that the person starts work at an odd time (say, 3AM). If I knew this person didn't go to sleep before starting work, I might ask:

How late did you stay up before going to work last night?

Your sentence asks about until/by + what time, but many of these questions are asked with "how long" (or "how late") instead, which is why it's hard to give you a straight answer to your question.

Here's a situation where I might use this phrasing. You and I plan to go camping this weekend. I need to get some details before we can finalize our plans. Later tonight, I'll start doing some research. That is the backdrop for this conversation:

After you figure things out, just give me a call, and let me know the plans, okay?
I can do that, but it might be kind of late before I get it figured out. Until what time can I call?
I should be up until 11; you can call me any time before then.
Sounds good.
If I haven't heard from you by that time, I'll look for a voice mail in the morning.

Until what time can I call? is asking how late it will be before it would be considered impolite to rouse you from bed with a phone call.


The first sentence is wrong. As for the second one, it isn't grammatically wrong, but as Jim has already told you it's isn't something a native speaker would say. You could say: "What time did you finish work last night?" As for "by/until" , they are both prepositions. Until= before the time when something happens and not after it.eg. "He worked for the company until he retired" It is rarely used in questions. "By"= no later than a specified time.eg. "You must finish the report by Friday afternoon."You won't see "by" used in the beginning of a question like the one you have written. You can say:"Had you finished work by 11:30 yesterday?'"" "Until what time did you stay up for work last night" can be written"= "Did you stay up until very late last night?"

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