code: public int length() {
  
          int days = 1;
          Weekday current = this.start;
  
          while (current != this.end) {
              days++;
              current = current.next();
          }
  
          return days;
  
      }
docs: /*[deutsch]
  <p>Ermittelt die Anzahl der Tage, die zu dieser Wochentagsspanne geh&ouml;ren. </p>
  
  @return  count of days in range {@code 1-7}