If the action had to be done on a certain date, you should have made it just an untimed calender item for that date. If the action could have been done on any date up to a deadline, you could put it on the @computer list and include the due date in the action list item discription. As the due date approaches, and you have not completed the action, I would transfer it from @computer to the calender as an untimed calender item.
Others may also use tickler (paper or computer) messages to remind them of actions with due dates in advance of the deadline to encourage completion of the action item ahead of schedule.
Hop this helps.