The system of flexible working hours has the objective to increase the competitiveness of the company (productivity) as well as improve the quality of life of the worker (more vacation leave) at the same time through an efficient distribution of working hours.
Since this system is based on the employment regulations of the company or the agreement between management and labor, the worker has to be able to predict the working hours.
If this system shall be applied also to working hours that were not planned, the worker would not be able to predict when to work and not, so that the regular life pattern would be disrupted. This would also lead to difficulties in terms of health and cultural life of the worker.
Accordingly, applying the system of flexible working hours to unplanned overtime work is not possible.