code: @Test public void timestampLocal() throws JoranException, IOException, InterruptedException {
    String sysProp="ch.qos.logback.classic.joran.JoranConfiguratorTest.timestampLocal";
    System.setProperty(sysProp,"");
    String configFileAsStr=ClassicTestConstants.JORAN_INPUT_PREFIX + "timestamp-local.xml";
    configure(configFileAsStr);
    String r=loggerContext.getProperty("testTimestamp");
    assertNull(r);
    String expected="today is " + new SimpleDateFormat("yyyy-MM").format(new Date());
    String sysPropValue=System.getProperty(sysProp);
    assertEquals(expected,sysPropValue);
  }
  