The customer would like the employees to start every day within a 2h time window. This window can (and will) be different for each employee and it is not pre-determined. Rather the software should try to ensure that ideally no employee starts a shift at say 7am and one at 10am (these are 3h apart). This functionality should be configurable in terms of the Duration between the earliest start and the latest start of a shift assigned to an employee and the Period for which this Duration should not be exceeded.