Switch calendar in schedule

Current Situation

• The run-time of a schedule is assigned a calendar, a period and optionally a restriction.
• It is not possible to switch calendar without loosing data. If a different calendar should be used, then the run-time entry must be deleted and must be re-entered.

Desired Behavior

• It should be possible to switch calendar in the run-time of a schedule without having to re-enter the period or the restriction.