The Dates component in Project System is used to plan and check the dates in project. The use of date scheduling is to determine phases in a project and duration of the phases, critical paths, and events in project schedule.
In Work breakdown structures WBS and Network, you enter the dates and these dates can be changed during full project lifecycle.
When you define a project in system, you enter the start and the finish dates of the projects. When you create Work Breakdown structure, you start planning dates for WBS. The dates are calculated for full part of part of project for activities using the scheduling function.