@Override
 public Time plus(Integer hour, Integer minute, Integer second, Integer nanoseconds) {
   DateTimeInterval interval = new DateTimeInterval(this);
   interval.plus(hour, minute, second, nanoseconds);
   return GregorianDateTime.newTime(
       interval.getResultHour(),
       interval.getResultMinute(),
       interval.getResultSecond(),
       interval.getResultNanoseconds());
 }
 @Override
 public Time minus(Time that) {
   DateTimeInterval interval = new DateTimeInterval(this);
   interval.minus(that.getHour(), that.getMinute(), that.getSecond(), that.getNanoseconds());
   return GregorianDateTime.newTime(
       interval.getResultHour(),
       interval.getResultMinute(),
       interval.getResultSecond(),
       interval.getResultNanoseconds());
 }