code: LocalDate withLocalMillis(long newMillis) {
          newMillis = iChronology.dayOfMonth().roundFloor(newMillis);
          return (newMillis == getLocalMillis() ? this : new LocalDate(newMillis, getChronology()));
      }
docs: Returns a copy of this date with different local millis.
  <p>
  The returned object will be a new instance of the same type.
  Only the millis will change, the chronology is kept.
  The returned object will be either be a new instance or <code>this</code>.
  
  @param newMillis  the new millis, from 1970-01-01T00:00:00
  @return a copy of this date with different millis