docs: public static DayOfWeek plus(final DayOfWeek self, int days) {
          int daysPerWeek = DayOfWeek.values().length;
          int val = ((self.getValue() + days - 1) % daysPerWeek) + 1;
          return DayOfWeek.of(val > 0 ? val : daysPerWeek + val);
      }