I always have a tough time with this. Suppose the following:

The software will be installed when the computer is ready.


The software will be installed when the computer will be ready.

Technically, both events are in the expected future (the computer being ready as a premise for the software being installed), but which one is right, or if they are both right, what nuance do they convey?

3 Answers 3


The first one is correct. The second is wrong.

The reason is that you cannot use the Simple Future tense in Time Clauses, so those ones that start with when, while, before, after, by the time, as soon as, etc.

In your case, the Present tense is adopted; so, the correct sentence is:

The software will be installed when the computer is ready.

  • See When here: esl.about.com/od/grammaradvanced/a/adverb_clauses.htm
    – z7sg Ѫ
    Apr 26, 2011 at 18:06
  • It says "Present or Past"... Progressive and Perfect are included in such categories, right?
    – Alenanno
    Apr 26, 2011 at 18:07
  • It's saying you can't use progressive with when, only simple past OR the present. It goes through each kind and there are different rules for different time clauses, for example, you can use past continuous (progressive) with while.
    – z7sg Ѫ
    Apr 26, 2011 at 18:15
  • I edited it to be sure it's correct... But honestly I saw on some site that also the perfect and the progressive were allowed. If I can find further reference, I'll post it.
    – Alenanno
    Apr 26, 2011 at 18:23
  • 1
    The rule is you cannot use the future in time clauses. If you want to use the progressive, and you want to be strictly grammatically correct, you should probably use while instead of when. But the when/while distinction is pretty subtle; if you ask a native English speaker When did you meet John? I think they would be much more likely to answer When I was visiting Boston. than While I was visiting Boston. But native English speakers are unlikely to say ... when it will be ready. Apr 26, 2011 at 19:10

The former.

It could even be rephrased to be a little more technically correct:

The software installation will begin when the computer is ready.

This correction goes for both instances of your phrase, since they both (kind of) indicate that the installation will be instantaneous - for example, depending on the computers readiness, that is when the software installation process can be decidedly successful / complete. If you're in a different situation then could you explain it in a little detail?

My reasoning for the latter being invalid is simply that it sounds plain wrong, inasmuch that 'when the computer is ready' is your condition for installation, 'when the computer will be ready' has a condition within a condition that can't necessarily be satisfied. There'll be technical terms, to be sure - but no doubt a linguist will notify me.

  • Actually, I wasn't aware that I would skew the answer with that context. I was not thinking of automation, even, just the plain matter-of-fact that software can only be installed on ready computers :P But the context is really just an excuse here.
    – MPelletier
    Apr 26, 2011 at 18:13

Both work and convey the meaning intended but a strict interpretation will find this difference between the two:

The software will be installed when the computer is ready. (After the computer is ready, the software will be installed.)

The software will be installed when the computer will be ready. (After someone decides that the computer will eventually be ready, the software will be installed.)

In other words:

Once we know task A will be finished we will begin on task B.

The distinction is mostly pedantic, however.

  • +1 oh, but that distinction is what contributes to the "mythical" in the "mythical man month" :) Apr 26, 2011 at 18:42

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