Future after when

[Katarzyna]

Test No. errors/elem-13 "Telephones", question 9

Soon will come a time when you want be able to do a lot of different things with your mobile phone.

(a) when
(b) want
(c) different things

Test No. errors/elem-13 "Telephones", answer 9

Soon will come a time when you will be able to do a lot of different things with your mobile phone.

Correct entry: will
The error was: (b) want
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"Soon will come a time when you will be able to do a lot of different things with your mobile phone."

Why is a future form used here after 'when'?
Could you explain it to me because the general rule say we don't use future after 'when'.
Thanks a lot

[Torsten]

Hi Katarzyna,

You are probably referring to those future time clauses that use when, if, before, after or until. For example:

When you arrive, I will call your boss.

Yes, in those clauses the verb after when, if, before, after or until is Present Simple,

However, you can use when in other future constructions. For example:

When are going to finish your paper?
When will you be able to answer my question?
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary

[Katarzyna]

Now I think I get it but I’m not sure.

For example:
1. He will tell me (---what I want to know----) when he has this book. (=I know WHEN he will tell me what I want to know - let's say tomorrow)
2. Tomorrow he will tell me when he will have this book. (= I know WHAT he will tell me )

Is my way of thinking good?
Thank you very much for your help, Torsten .

[Torsten]

Yes Katarzyna, your first sentence is a clause with when and the when sentence is in Present Simple. Look at this example:

Mike will tell me what he thinks of your book when he gets it from you.

In this sentence it's clear that Mike can tell me his opinion on the book only after he gets the book.

Mike will tell me when you are going to give your book to him.

So, in the second sentence I want to know when (today, tomorrow, next week?) Mike will get the book from the other person.
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Test Of English for International Communication
TOEIC Preparation & TOEIC Vocabulary

[Katarzyna]

Many thxs, Torsten