Can anybody explain this with example?

I read this on the internet : Never use "will" in the clause where you use "while/when/before/after/by the time/as soon as/if/unless".
For example :
I will call you when I will arrive. (Incorrect)
I will call you when I arrive. (Correct)

I am a little confused about its usage. Does it mean wherever we use "while/when/before.....", we shouldn't use the future tense in that clause? What is the actual meaning of time clause here?

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The rule is very simple meg: Use the present simple in clauses introduced by when, as soon as, until, after, before and while.

Ps - You may also need to use the present perfect in some cases when you need to show that one action can only take place after another has been completed, as in: "As soon as I've eaten this meal, I won't feel hungry any longer."
Dear meg,
The rule is very simple.
First let me come to the meaning of WILL. It means an affirmation to do something (or to not do something). When I say "I WILL call you", it means that I have promised to do something (in this case, "call you.)
Now coming to the use of WILL while using "while/when/before/after/by the time/as soon as/if/unless". If you will note, all these are future tenses. All these are yet to happen. When I say "I will arrive" it means I am certain of my arrival. How can anybody be certain of the future. I may never arrive. This is the reason why the use of WILL (which is confirmatory in nature) is prohibited with things/events to happen (the future is uncertain).
I hope this helps you.
If it is not clear, I WILL do it when I WILL write the next time. (Got the message--I may not write at all.) So, the correct usage is "If it is not clear, I WILL do it when I write the next time.
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The important thing here is to see the difference between a 'sentence' and a 'clause'. The time clause in your second example is 'when I arrive' and that is the part of the sentence in which you can't use 'will'.
Dear all,
Thank you so much for your help. Now I got it correctly.
Never use "will" in the clause where you use "while/when/before/after/by the time/as soon as/if/unless".

1. "Never" is a strong word! Emotion: smile

2. Since 'if' and 'unless' do not introduce time clauses, we can't conclude that only time clauses are included in the "rule" - only that the "rule" applies to certain subordinate adverbial clauses, usually, but not always, related to temporal relations. The list of subordinating conjunctions given is representative, but not complete.

3. "will" is not the only word not to be used in the subordinate clause in these cases. A more complete list is "will", "would", and "going to".

4. Examples:

Helen won't go unless Bill goes, too. Emotion: smile
Helen won't go unless Bill will go, too. Emotion: sad

Keep reading until you reach the end of the paragraph. Emotion: smile
Keep reading until you're going to reach the end of the paragraph. Emotion: sad

I'd better mail these packages before I forget.Emotion: smile
I'd better mail these packages before I will forget. Emotion: sad

Larry and Peter said they would stop by after they bought the tickets. Emotion: smile
Larry and Peter said they would stop by after they would buy the tickets. Emotion: sad
They would stop by after they had bought the tickets.Emotion: smile
They would stop by after they would have bought the tickets. Emotion: sad

5. Exceptions.
a. The rule does not apply to "when" as a question word.

When will you be home from work tonight?
When is Cheryl going to buy the car she likes so much?

b. The rule does not apply to "when" or "if" when they introduce an indirect question. (In these sentences, "whether" can replace "if".)

No one knows when an earthquake will occur.
I didn't know if I would feel like eating that early.
We needed to find out if George would help us.

c. The rule is relaxed after "before" in certain idiomatic expressions of will, i.e., willingness or willfulness -- expressions which combine volition with futurity. Note that there is sometimes a shade of exasperation expressed by the speaker. Both elements of the pairs shown are acceptable (in my opinion) in casual speech.

I've finally stopped the children from fighting,
but it won't be long before they'll be at it again.
but it won't be long before they're at it again.

Janice got in a car accident when she ran a red light.
It will be a long while before she'll try that again.
It will be a long while before she tries that again.

Ken gave me very bad advice,
but it was a long time before he would admit he was wrong.
but it was a long time before he admitted he was wrong.

It will be a cold day before I'll let my daughter marry that man!
It will be a cold day before I let my daughter marry that man!
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Thank God! I didn't feel faint while reading that much. <--- joking
Hey Jim! Thanks a millon! How kind of you writing all this detail!
Anyway, I am planning to start to take English lessons from you. Where do you live? You really have extensive knowledge of English. My hat off to you!
Emotion: smile I do tend to rave on with my little novelettes! Please don't faint!
Thanks for the vote of confidence. Where do I live? 95124
Thank you, CalifJim, for your very clear and very useful explanations.

1. I agree with you, and I don't like the oversimplified, formalistic way of expressing grammar rules, as: "Never use... after...": as you said, "never" is a strong word!
Teachers sometimes seem to think that, if they explain things a little better, their pupils will be confused; but the truth is that pupils think (some of them at least), and they'll be disappointed when they see (here's our rule!) that the pseudo-rules they've learned are hardly ever true: which is not the fault of the rules themselves, but of the unaccurate and false way of expressing them. Of course, we mustn't be unnecessarily complicated, but I think that it's important to be accurate.

2. As for this rule, perhaps I would express it so: "Whenever, in a sentence, the main clause contains a future tense, the dependent (subordinate) clause cannot contain a future, too: its verb must be a present".
What do you think of this formulation? I think that it might be accurate enough for practical, didactic purposes.

3. Here's an example of how I'd explain it:
"When I get back home, I'll read your letter."
Here we have a sentence, with a main clause: "I'll read your letter", and a dependent clause: "When..."; since the future ("I'll...") is used in the main clause, it can't be used in the dependent clause: "When I shall (I will, I'll) get back home, ..." would be wrong; we must use the present instead: "When I get..."

4. This rule is particularly important for those students of English whose mother tongue is one that would use two future tenses in such sentences: both in the main and in the dependent clause. That would be the rule, for instance, in Italian.
I would then explain the thing with a comparative (contrastive) method: I would ask my pupils: "How would you say that in Italian (French, Spanish, etc.)?", and I'd point out the difference: two future tenses in their mother tongue, only one (in the main clause), and a present (in the dependent clause), in English.

5. If we express the rule like that, we needn't enumerate the conjunctions after which, or the clauses in which, the future tense mustn't be used.
These are mostly temporal or conditional clauses; but I think that it would be wrong to say, e. g., *"The first who will get back home, will read the letter": it should be "...who gets"; and this is a relative clause.

6. What do you think of this? English isn't my mother tongue, and I'm only trying to learn it.
And now, on second thoughts, I'm not sure that my formulation was right: perhaps it's too general; for example, would this sentence be wrong: "Next year I'll be very sad, because you won't be with me any more"? Should it be "...because you aren't..."? I don't think so. So, perhaps IT IS necessary to enumerate the clauses in which the future would be uncorrect.

7. Just one more question. Please, bear with me (my heart is in the coffin).
Both "shall" and "will" can be used as auxiliary verbs to form the future tense, but they can also mean "must" and "want" respectively. So, would it be possible to use them in a dependent, e. g., if- or when- clause (with a future in the main clause), with these second meanings? I think I've found some such sentences, but I'm not sure, and I can't think of an example now: could you give me one (or two)?

Thanks for your patience, and for your precious help.
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