I would love the timestamps feature as well. The timestamp could go where we have the due date. When the user complete the task, the timestamp will replace the due date with "completed on MM/DD/YY at HH: MM." If the user completes the task late, the time stamp could be colored in red; if the task is completed on time, the timestamp is colored in green. In both instances, if you click on the timestamp, it should have all recorded changes as a dropdown.