Hello, fellas. In this session we will learn how to express the future in time clauses.
A time clause is an adverb clause beginning with such words as when, before, after, as soon as, until, and while. However, will or be going to is not used in a time clause. The clause carries future meaning despite its simple present tense.
Dave will arrive soon. When he arrives, we will see him.
Sometimes a time clause uses the present progressive to express an activity that will be in progress in the future.
While I am studying overseas next year, I am going to visit several tourism destinations.
To emphasize the completion of the act before the other act takes place in the future, the present perfect is used in a time clause.
She will take a rest after she has finished her project.
Betty Schrampfer Azar, Understanding and Using English Grammar: Third Edition