DaleHoward, thanks for your reply.

So, if I understand correctly, the structure is:
- Working time in: Project Settings are the basis for calculations in the planning
- You can have these settings implemented in your standard calendar.
(Change settings not only for the project but for all new projects)
The start- and end-times are shown in the Work Time Changes dialog
- Your project calendar becomes a new calendar for your project and is a copy of your Standard Calendar
(which you just have set)
- Resource calendars are copies of the selected calendar (Worktime Change is based on .... )
- If you have adjusted working hours at Resource calendar, it will be used for lead (calculated) time
- If you have adjusted the working time of the Project calendar,
these working hours will be used for lead (calculated) time