Absolute Completion Date
When you tell your children you want their homework done by six o'clock, knowing you really want them finished by seven, you're setting one time for their benefit and a second one for yours. Likewise, you know the last possible date something can be completed on the project, but that is not the date you put down on the network diagram or tell the person doing the task. If you're printing a special end-of-year holiday brochure to come out in November, you may tell your copywriter that you need all copy in by September 15th, knowing that it won't be sent to the printer until September 30th.
Make sure team members know when their work needs to be completed. This is especially important when the start of one task depends on the completion of another.
You should have a completion date for each task and an absolute drop-dead completion date, which is when the work absolutely, positively must be finished. Promote your deadlines and keep your absolute deadline in a separate place. Just as budgets get padded, so do schedules. Often the manager or boss who must have it tomorrow really doesn't need it until the day after — she's just not providing you with that information. By determining the latest a task or activity can be completed without interfering with the overall project, you have some room to maneuver when you need to make adjustments to the schedule.
The same holds true for a start date. What is the date you plan to start an activity? If there are delays, what is the absolute latest date you could start the activity and still get it completed in time to keep the project running on schedule? You may have to look at other tasks to determine this because other tasks may be dependent on this work getting started and completed at a certain time.
If you're not sure how long something should take to accomplish, get the best and worst time frames and use the average number plus 10 percent. If, for example, one source indicates that you can get all the necessary supplies to Boston in seven hours, but another source says that with heavy traffic it has taken as long as nine hours, you might take the average of the time estimates and come up with eight hours. Add 10 percent to play it safe and you have 8.8 hours, which rounds off to nine hours for your time estimate.