code: public StringBuffer format(Calendar calendar, StringBuffer buf) {
          if (mTimeZoneForced) {
              calendar.getTime(); /// LANG-538
              calendar = (Calendar) calendar.clone();
              calendar.setTimeZone(mTimeZone);
          }
          return applyRules(calendar, buf);
      }
docs: <p>Formats a <code>Calendar</code> object into the
  supplied <code>StringBuffer</code>.</p>
  
  @param calendar  the calendar to format
  @param buf  the buffer to format into
  @return the specified string buffer