code: public static final DateIntervalFormat getInstance(String skeleton, 
                                                     DateIntervalInfo dtitvinf)
      {
          return getInstance(skeleton, ULocale.getDefault(Category.FORMAT), dtitvinf);
      }
docs: Construct a DateIntervalFormat from skeleton
  DateIntervalInfo, and the default <code>FORMAT</code> locale.
  
  This is a convenient override of
  getInstance(String skeleton, ULocale locale, DateIntervalInfo dtitvinf)
  with the locale value as default <code>FORMAT</code> locale.
  
  @param skeleton  the skeleton on which interval format based.
  @param dtitvinf  the DateIntervalInfo object to be adopted.
  @return          a date time interval formatter.
  @see Category#FORMAT