code: public static final synchronized void useValueFormat(String pattern)
  	{
  		if (pattern == null)
  			sdf = null;
  		else if (sdf == null) {
  			sdf = new SimpleDateFormat(pattern);
  			sdf.setCalendar(getCalendar());
  		}
  		else
  			sdf.applyPattern(pattern);
  	}
docs: Sets a user defined time value format used by all instances of this class.
  <p>
  The pattern is specified according to {@link SimpleDateFormat}. Subsequent time
  information, supplied and returned in textual representation, will use a layout
  formatted according this pattern.<br>
  Note, the format will rely on calendar default time symbols (i.e. language for
  example), and does not support the KNX DPT identifier "no-day" for day of week.
  This identifier can not be used therefore.
  
  @param pattern the new pattern specifying the value time format, <code>null</code>
  to reset to default value format