code: @Override
      public int compare(
          LeapSecondEvent o1,
          LeapSecondEvent o2
      ) {
  
          GregorianDate d1 = o1.getDate();
          GregorianDate d2 = o2.getDate();
  
          int y1 = d1.getYear();
          int y2 = d2.getYear();
  
          if (y1 < y2) {
              return -1;
          } else if (y1 > y2) {
              return 1;
          }
  
          int m1 = d1.getMonth();
          int m2 = d2.getMonth();
  
          if (m1 < m2) {
              return -1;
          } else if (m1 > m2) {
              return 1;
          }
  
          int dom1 = d1.getDayOfMonth();
          int dom2 = d2.getDayOfMonth();
  
          return (dom1 < dom2 ? -1 : (dom1 == dom2 ? 0 : 1));
  
      }
docs: /*[deutsch]
  <p>Vergleicht zwei Schaltsekundenereignisse nach ihrem Datum in
  aufsteigender Reihenfolge. </p>
  
  @param   o1  first leap second event
  @param   o2  second leap second event
  @return  {@code -1}, {@code 0} or {@code 1} if first event is before,
  equal to or later than second event
  @since   2.3