private void parseDate(String aDate) {
    Matcher matcher = DATE.matcher(aDate);
    if (matcher.matches()){
      String year = getGroup(matcher, 1, 4, 6);
      if(year !=null ){
        fYear = Integer.valueOf(year);
      }
      String month = getGroup(matcher, 2, 5);
      if(month !=null ){
        fMonth = Integer.valueOf(month);
      }
      String day = getGroup(matcher, 3);
      if(day !=null ){
        fDay = Integer.valueOf(day);
      }
    }
    else {
      throw new DateTimeParser.UnknownDateTimeFormat("Unexpected format for date:" + aDate);
    }
  }