public final void setTransientEnabledOnDates(boolean enabled, UTCDate date) {
        assert isDateVisible(date) : date + " must be visible";
        getView().setEnabledOnDate(enabled, date);
    }
Sets a visible date to be enabled or disabled. This is only set until the
next time the DatePicker is refreshed.
stroom-core-client-widget/src/main/java/stroom/widget/datepicker/client/CustomDatePicker.java