code: public void updateTimeZone(String timeZone) throws SecurityException {
  	checkWriteAccess();
  	boolean hasAccess = ConfigWebUtil.hasAccess(config, SecurityManager.TYPE_SETTING);
  	if (!hasAccess) throw new SecurityException("no access to update regional setting");
  
  	Element regional = _getRootElement("regional");
  	regional.setAttribute("timezone", timeZone.trim());
  
      }
docs: update the timeZone
  
  @param timeZone
  @throws SecurityException