private String translateViewName(String viewNameOld) {
        switch (viewNameOld) {
            case "month":
                return "dayGridMonth";
            case "basicWeek":
                return "dayGridWeek";
            case "basicDay":
                return "dayGridDay";
            case "agendaWeek":
                return "timeGridWeek";
            case "agendaDay":
                return "timeGridDay";
            default:
                return viewNameOld;
        }
    }
Translates old FullCalendar-ViewName (<=V3) to new FullCalendar-ViewName (>=V4)
@param viewNameOld
@return
primefaces/src/main/java/org/primefaces/component/schedule/ScheduleRenderer.java