Fill in the blanks to complete the procrastinating student's very optimistic promises to their roommate.

Don't worry, by midnight I will have written all twenty pages of this history essay.

And by the time you wake up tomorrow morning, I will have submitted it to the professor!

Don't worry, by midnight I will have written all twenty pages of this history essay.

We use the future perfect to show that an action will be entirely finished by a particular point in the future (midnight).

And by the time you wake up tomorrow morning, I will have submitted it to the professor!

The phrase "by the time" is a strong clue for the future perfect. The submission will be a completed action before the roommate wakes up.