|If the action will be completed by a certain moment in the future
Melody's working day ends at six o'clock. At six-fifteen, she will have gone home.
— Will Mary be at the party by midnight? — No, she will have left by that time.
— Will you be having lunch at 2 pm? — No, we'll have finished by that time.
It will be raining in the afternoon, but it'll have stopped raining by five o'clock.
|With stative verbs (be, know, live etc.):
to say that the action has been going for some time to a certain point in the future.
On the second of March, we'll have been married for one year.
On Friday, she'll have lived here for one month.