When someone says "I need x by Friday", I usually take it to mean they want x in their hands when Friday begins. However, when that same person says "I need x on Friday", I understand them to mean they want x no later than the end of the day Friday.
What about "I need x for Friday"? Is "for" in this context synonymous with "by" or "on"?
Do other people understand "due by" and "due on" in the same way I do? Is there a common consensus?