As Boyan mentioned in the current version of RadScheduleView by design in the TimelineView the DayStartTime
property applies only for the first visible day and the DayEndTime
applies only to the last visible day of the view. It is not possible to force the DayStartTime property to be applied to each day of the view because this is done in the code of the control.
We can advice you to use the Day/WeekViews and set the VisibleDays value to the desired size.
the Telerik team