The tasks (task: An activity that has a beginning and an end. Project plans are made up of tasks.) are not rescheduled when you change the project to schedule from a finish date (finish date: The date that a task is scheduled to be completed. This date is based on the task's start date, duration, calendars, predecessor dates, task dependencies, and constraints.).
When you choose to schedule a project from a finish date, you should examine the effects on any tasks that are already in the project. If you initially scheduled your project from a start date (start date: The date when a task is scheduled to begin. This date is based on the duration, calendars, and constraints of predecessor and successor tasks. A task's start date is also based on its own calendars and constraints.), the tasks were created with an As Soon As Possible (ASAP) constraint (constraint: A restriction set on the start or finish date of a task. You can specify that a task must start on or finish no later than a particular date. Constraints can be flexible [not tied to a specific date] or inflexible [tied to a specific date].) by default. When you change your project to schedule from a finish date, all new tasks will be created with an As Late As Possible (ALAP) constraint by default. However, the original tasks still have ASAP constraints that can affect when the tasks are scheduled as you enter actual (actual: Information that shows what has actually occurred. For example, the actual start date for a task is the day that the task actually started.) start and finish dates. This can create unnecessary negative slack (slack: The amount of time that a task can slip before it affects another task or the project's finish date. Free slack is how much a task can slip before it delays another task. Total slack is how much a task can slip before it delays the project.) on the tasks if the tasks start late.
The amount of slack in your schedule tells you how much you can delay tasks before other tasks or the project finish date is affected. Total slack (total slack: The amount of time that the finish date of a task can be delayed without delaying the finish date of the project.) is the amount of time that a task can slip (slippage: The amount of time that a task has been delayed from its original baseline plan. The slippage is the difference between the scheduled start or finish date for a task and the baseline start or finish date.) before it delays the project finish date. When the total slack is negative, the task duration is too long for its successor (successor: A task that cannot start or finish until another task starts or finishes.) to begin on the date required by a constraint.
Examine the task constraints for all your tasks, and change ASAP to ALAP wherever appropriate.
Change task constraints from ASAP to ALAP
- On the View menu, click Gantt Chart.
- Click the field to the right of where you want to insert the new field. For example, click the Task Name field to insert the field immediately to the left of the task's name.
- On the Insert menu, click Column.
- In the Field name box, click Constraint Type, and then click Best Fit.
- To identify any tasks that have ASAP constraints and, if appropriate, change them to ALAP constraints, click AutoFilter .
- Click the AutoFilter arrow in the Constraint Type field heading, and then click As Soon As Possible.
- Click the arrow in the Constraint Type field of the first task displayed, and then click As Late As Possible.
- Point to the lower-right corner of the field. When the pointer changes to a plus sign, drag down to set the fields for all the tasks to As Late As Possible.