The basis for a schedule in project management is often the work breakdown structure. A schedule displays the project’s start and its expected completion date, as well as the start and end date and estimated duration of summary activities, activities, milestones, and tasks. Scheduling also takes into account dependencies, constraints, and buffer times between activities. The more accurate the estimations are, the better can risks be identified and, in the best-case scenario, be prevented. For project managers, the schedule is the basis for project controlling and represents the optimal course of the project. During the project, the schedule often has to be adjusted, e.g. due to unforeseen events that cause delays. Important deadlines that must not be postponed without postponing the project's completion date can be identified using the critical path method.