Constraints, deadlines, and entered dates
Constraints and deadlines both mention dates, but they do different jobs. A constraint is scheduling logic; a deadline is normally a target to monitor.
Constraints restrict the calculation
Section titled “Constraints restrict the calculation”A constraint limits when an automatically scheduled task can start or finish. Project groups constraints into three broad behaviors:
- Flexible constraints such as As Soon As Possible and As Late As Possible leave the engine room to work around other information.
- Semi-flexible constraints require an earliest or latest date.
- Inflexible constraints such as Must Start On or Must Finish On anchor the task to a specified date.
Use a constraint when the date is a genuine scheduling rule. A hard-coded date entered only because it was visible in an earlier plan can restrict later calculations unexpectedly.1
To add a constraint, select the task in the Gantt Chart, choose Task > Information > Advanced, select a Constraint type, and enter a Constraint date when the selected type requires one. Project Plan 365’s Apply Constraints article covers the equivalent workflow in that product.
Deadlines are targets
Section titled “Deadlines are targets”A deadline normally does not move the task. It gives Project a target to report if the task is late. A deadline inside a task’s available slack can change total slack and make the task appear critical; that does not turn the deadline into a hard constraint.
You can set deadlines for individual tasks and summary tasks. For an individual task, select it and choose Task > Information > Advanced, then enter a date in Deadline. To track an overall project target, show the Project Summary Task from Format > Show/Hide > Project Summary Task, select that row, and set its Deadline the same way. If the project summary deadline conflicts with subtasks, Project flags the missed deadline on the summary task.2
Project Plan 365 offers a different project-level option: set the overall deadline directly in Project > Project Information > Deadline. See its deadline guidance.
Entered dates
Section titled “Entered dates”For an automatically scheduled task, Project can calculate duration from the working time between entered start and finish dates. Entering dates can also add constraints that compete with dependencies and calendars.
For a complete view of how these inputs interact, see How Microsoft Project schedules tasks. For task entry and duration guidance, see Create and Edit Tasks.