No, time is not the issue. The problem is completion of a neverending series. Look at it this way. If I have a finite number of tasks, I can finish them because with each one I have fewer left to do. At some point I have 5 left, then 4, then 3, then 2, then 1, and when I get that task done then I've finished the series. I complete the series as a whole by completing it's final element. But an infinite series cannot be completed this way. I can't complete it by getting to the end of it. But if I can't get to the end of it, in what sense can I complete it? Remember, I have to do the tasks one at a time. And no matter how many tasks I complete, there are still infinitely many left to do. I understand that the total time spent working on the series is finite because each task takes less time than the previous. I understand how calculus can determine a least upper bound to the time spent. But calulus cannot explain how it is we reach the end of a series that doesn't have one. And that is the real puzzle.