How about catching a movie tonight? It starts at 9pm. Our working day ends at 8:50 pm. The movie will have started by the time we get to the theater as it'll take us 20 minutes to get there.

One resource says that with phrases such as "before" and "by the time" you can often use future simple and future perfect interchangeably.

Can I use Future Perfect and Future Simple interchangeably in the above example?

I realize now that you can use future simple if you assert something or, in other words, intend to do something by some time in the future, as in:

"I will do my homework by 9pm"

  • It's fine. Yes, either before or by the time are fine. You cannot use the simple future here (in your movie example).
    – Lambie
    May 14, 2021 at 17:58
  • 1
    The sentence you quoted works, and is idiomatic. It may be possible to say the same thing in a better way; but, I've heard this sentence used by native speakers (with very minor alterations). Yes, it would be nice to say "the movie will start before we get to the theater", but in English there is often more than one way to correctly say the same thing.
    – Edwin Buck
    May 14, 2021 at 20:00

1 Answer 1


If something has not yet happened in the future. 1)

  • The movie will have started by the time we get to the theater as it'll take us 20 minutes to get there. [FUTURE perfect]

There is an event preceding the getting there in the future: the event is that the movie started before you got there.

Think of it as parallel to: 2)

  • The movie had started by the time we got there. [PAST perfect]

Think of a timeline (everything in English verbs happens on a timeline]


[Notice the parallelism of the tenses in relation to the present time. Both of them involve another event. The trick is: Sometimes the event is implied and is not stated outrightly.]

Although by the time we get there is present tense, the meaning is future. So anything that comes after it has to be in the future perfect.

[Yes, it can be either before we get there or by the time we get there]

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