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Future simple :
We will finish the project by next year

Future perfect :
We will have finished the project by next year

I've been told that Future perfect must be used when 'by' exists. But for some reason, future perfect doesn't seem natural to use here. Perhaps due to my years of bad spoken english experience. May I ask which tense to use when somebody asks about the time it takes to finish a project ?

marked as duplicate by Edwin Ashworth, Kris, Community Feb 5 '18 at 12:54

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  • 4
    Please cite the authority that claims by must be used with the future perfect, as well as the actual wording of the claim itself. As presented, it isn't correct - there's nothing wrong with the grammar of "We will finish by the evening" or of "We would have finished by the evening had things gone to plan". – Lawrence Feb 5 '18 at 8:52
  • @Lawrence - I'm coming from this video . In that he uses the exact same example in future perfect. For me, it looked a bit odd to use future perfect for the stated situation, so I've asked about the same here... – rsadhvika Feb 5 '18 at 9:21
  • The future perfect works with by in his second example, but I wouldn't elevate it to a 'rule'. – Lawrence Feb 5 '18 at 9:34
  • Thank you @Lawrence I think I see now why it is just a guideline and not a rule. It's to do with the semantics I guess. Future perfect seems to convey something will be done before some date, and this date has some pre existing special meaning to everyone involved.) – rsadhvika Feb 5 '18 at 9:41
  • In future simple the date has no special meaning. It could be any date... I may be wrong, but this contrast between both the tenses fits with my model... Do you maybe suggest any simple grammar book which emphasizes differences like these ? – rsadhvika Feb 5 '18 at 9:48

A quote from Cambridge Advanced Grammar in Use, 2002 Unit15: "We use the Fut.Perfect to say that something will be ended, completed, or achieved by a particular point in the future."

So you can use this tense if you want to stress the idea of completeness. Yes, 'by' could be a useful signal, but the presence of 'by' doesn't mean that you MUST use a particular tense.

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