code: public static String format(final Calendar calendar, final String pattern, final TimeZone timeZone) {
          return format(calendar, pattern, timeZone, null);
      }
docs: <p>Formats a calendar into a specific pattern in a time zone.</p>
  
  @param calendar  the calendar to format, not null
  @param pattern  the pattern to use to format the calendar, not null
  @param timeZone  the time zone  to use, may be <code>null</code>
  @return the formatted calendar
  @see FastDateFormat#format(Calendar)
  @since 2.4