In most subordinate clauses we can't use "will" to refer to the future. This is usually true after conjuntions of time, question words, if, whether and in defining relative clauses.

However, in these cases, we can use present simple or present perfect instead. I wonder if there is any difference between them. For example:

We'll have a party when we take our exams.


We'll have a party when we've taken our exams.

I'm not talking about tenses after hope, bet, as, than, because, although, since and cases where the use of "will" in subordinate clauses is necessary.

  • 1
    Hi! Yes, the difference is the difference between simple and perfect. Please edit to show that you've looked up a little bit about these tenses and what you already understand. Nov 9, 2023 at 19:32
  • @AndyBonner The present simple normally refers to a generally repeated action or an ongoing state, and present perfect normally refers to a past event. But in these time clauses, they refer to one-time future events, so knowledge of those functions alone wouldn't help the OP understand the meaning here. THAT SAID, there is a lack of information about what the OP already knows about time clauses with "when".
    – gotube
    Nov 9, 2023 at 21:05
  • Kaymond, Are you asking about those tenses in all subordinate clauses, or just in subordinate clauses of time, or just in subordinate clauses of time with "when"? And as Andy said, before we can answer this, we need to know what you already understand about the topic (whichever topic it is), and exactly what part of it you're unsure about. So I'm closing this question (for now) to new answers. Please edit this information into your question, and then put "@gotube" in a comment so I can reopen the question. Thanks!
    – gotube
    Nov 9, 2023 at 21:06
  • @gotube added more information!
    – Kyamond
    Nov 9, 2023 at 22:59
  • 1
    @Kyamond Great work! More of that kind of question please!
    – gotube
    Nov 10, 2023 at 6:51

1 Answer 1


The difference is that with present simple the clause refers to the time when the event starts, but with the present perfect version, it refers to the time when the event is finished.

So your sentence with present simple means we will have a party while taking our exams, and with present perfect means we will have a party once our exams are over.

The intended meaning is probably the second one, but the first sounds like fun too.

  • Thank you. May I ask whether you have any sources for your answer?
    – Kyamond
    Nov 10, 2023 at 10:01
  • @Kyamond Other than being a native speaker and being 100% confident, no, I don't have any sources to back this up. Here's one place that agrees with me, but they're not authoritative: test-english.com/explanation/b1-2/when-i-do-vs-when-i-have-done
    – gotube
    Nov 10, 2023 at 21:01

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