Some schedules require appointments that exceed midnight (for discussion's sake, a company that operates night shifts to accommodate customers on the other side of the world). In this case I would like the "Monday" column to start at Monday 6pm to Tuesday 7am.

This is instantly doable in WPF RadScheduleView by setting the property. I would expect this to be useful here as well, since there's an EndTime property it just needs to be expanded to display appointments correctly.