Ron Rosenhead has a great post about Bring Back The Meaning of Deadlines. The use of deadlines is common in project management. It's part of the culture of projects to speak about Milestones, Deadlines, and single items like that.
But here's the rub. Let's start with the Douglas Adams quote.
I love the sound deadlines make as they whoosh past
For the majority of deadlines and milestones, there is no entry or exit criteria for these "single point" items. By single point in mean a deadline or a milestone.
So here's the problem. When the project has milestones or deadlines, there is no explicit statements about what it means to arrive at the milestone or deadline, pass the deadline, be far away from the deadline or milestone. Or really anything about this "thing" that is in the schedule.
It's just a date or a rock on the side of the road, that you see as you go Whooshing by.
Now MSFT Project has this nice feature around Deadlines. They can be set for a date. We use this all the time in the IMP/IMS world for the Program Events. The PDR (Preliminary Design Review) for example has a planned date. The government usually sets this date and we put it in the IMS as a deadline. The Significant Accomplishments and Accomplishment Criteria, and the Work Packages and Planning Packages hang from this Program Event to the left, with the Deadline set.
In an assessment of the IMS the planned finish of the Program Event, say PDR, MUST be on or before the Deadline date, other we're late. But better the planned finish must be on or before the scheduled finish + the schedule margin for the Program Event.
With this condition we now have a credible IMS, with margin, a planned finish and a known "deadline" that has a credible probability of being met. 80% confidence level is typcially what we shot for with the applied schedule margin.
So use deadlines, use milestones. Just don't treat them as fixed rocks on the side of the road. Treat as warning indicators that your plan and master schedule is no longer credible, if you start to push the schedule margin below the allocated margin at a specific point in time.
