help !!!!! future or not?

[hannahm]

I 'll return the newspaper when I have looked through it."
Are they both future clauses? Or is the first future and the second past ?

Why is it not "I'll return the newspaper when I will have looked through it"
In this case are both future?

[Alan]

The main clause (I'll...newspaper) is in the future tense, while the subordinate clause(when...it) is in the present perfect, although its reference is to a future time.

This is the standard pattern for this kind of sentence in English, where adverbial time-clauses of future reference accompanying main clauses in a future tense do not take future forms, but either present or (as here) perfect.

The second sentence is, by virtue of the above rule, incorrect!