What does "it's due tomorrow."

The homework is due by tomorrow.
I'm due at his office at 4:30

What does "due" in these sentences mean?
The underlying idea is that there is a deadline.

eg The homework has to be given to the teacher by tomorrow.
eg I have to be at his office by 4:30 tomorrow.
It has to be done by tomorrow at some specified time.

For example, if your class starts at 6 pm tomorrow, and the homework will require one hour to complete, then you can start any time between now and 5:00 pm tomorrow.
Students: We have free audio pronunciation exercises.
"It's due tomorrow."
Does it mean it has be done tomorrow?
 AlpheccaStars's reply was promoted to an answer.
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What about this?
It's due on friday.
Does it mean it has to be done by friday?
Amir OghlowIt's due on Friday.
What time on Friday? There must be a time so you can determine if you are late or not.
Otherwise, if it's due on Friday, I would submit it on Thursday (or earlier), so there is no doubt about its being late.