Say something (a bill, a task request) has a deadline of May 1st. It's pretty clear that on May 2nd, it's overdue. What's less clear, and is leading to some arguments where I work, is: at what point is it "due"? As soon as it's assigned/generated? Two weeks before the deadline? Midnight on April 30th?
Edit: to clarify, the debate centers around when is it correct to start using the term "due". We've been using it to label tasks about 2 weeks to a month before the due date, and some people are saying that that is misleading, because those tasks are only "available" that early, but aren't due until... well, some nebulous time closer to the due date. (Which leaves the rest of us wondering why the word "overdue" bothers to exist.)