private String amPmIndicator(Integer aHour){
    String result = "";
    if(aHour != null){
      if(fCustomLocalization != null){
        result = lookupCustomAmPmFor(aHour);
      }
      else if (fLocale != null) {
        result = lookupAmPmFor(aHour);
      }
      else {
        throw new IllegalArgumentException(
          "Your date pattern requires either a Locale, or your own custom localizations for text:" + Util.quote(fFormat)
        ) ;
      }
    }
    return result;
  }