Future time clauses

In time clauses that refer to future time (clauses with if, when, after, before, as soon as, once, until, while etc.) we use the present tenses:

Say hi from me if you see him. (present simple)
Will you wait for me until I get back? (present simple)
As soon as I arrive, I'll give you a call. (present simple)
You can play in the garden when you have finished your homework. (present perfect)
I'll be waiting outside while you are speaking to the doctor. (present continuous)