A backlog is work that you haven't done yet, it's not belated until you have done it and turned it in after the deadline. Your backlog may not even be late.
You get one piece of work each day of the week.
They are all due on Friday.
If you wait until Friday to start, you have a backlog of four items (the item you could have done on Monday, the item you could have done on Tuesday, ...) and one current item.
You finish the first four items on Friday and turn them in. They were your backlog but you finished them on time.
You turn in the last item on the following Monday. It is late. It is a belated item, but was never part of your backlog (it was always the current item, the item on top of your stack of work).