I have always thought that the correct one is "I have to do it by tomorrow" as "by" is used for some point in the future while "until" is used when something longs until now/that time. Is that correct?

1 Answer 1


No, that is not really correct.

Doing something 'by' tomorrow means that the deadline for completion is tomorrow. This is delivery focused - aiming to complete a task, write a report, deliver a product etc.

Doing something 'until' tomorrow means you continue carrying out the activity until tomorrow. This doesn't imply a deliverable or an end product.

  • Thanks, but for example "I need that report by Friday" is definitely "by" - I cannot spot the difference between this and the one in the example. Also "I have to do it by tomorrow" is not grammatical? Because it has much mroe hits on Google than "until".
    – SilkySand
    Commented Jan 29, 2014 at 11:07
  • They are both grammatical but mean entirely different things. You would not say, "I need that report until tomorrow" (well, you could, but that would imply you are giving it back tomorrow...)
    – Rory Alsop
    Commented Jan 29, 2014 at 11:08
  • Oh righ, it would mean "I need to keep the record until tomorrow". So which one is actually correct - I have to do my homework until/by Friday?
    – SilkySand
    Commented Jan 29, 2014 at 11:10
  • I have to do my homework by Friday. I have to carry out the activity to produce that homework until Friday.
    – Rory Alsop
    Commented Jan 29, 2014 at 12:13

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