Nurse scheduling is a complex planning task in which many constraints, e.g. meeting the required demand or considering employees’ satisfaction, are considered. However, employee absences due to uncertain events require rescheduling of former planned optimal schedules, which is often impossible without exceeding some of previous assumed limitations. Within this paper, we evaluate the ability of planned schedules to react to changes during the planning horizon. We present a discrete event-driven simulation system to emulate shifts and assignment of nurses and include real-world data schedules as well as different rescheduling strategies, which address staff shortage. To gain insights in the schedules’ practicability, their effects regarding employee satisfaction, extra hours and additional costs are evaluated. First numerical experiments show that it is hard to find any substitution in case of an unforeseen absence. Thus, rescheduling with constraint relaxation generates significantly better results regarding the use of temporary staff and costs.