code: private void updateAccessInformation(final SecurityContext securityContext, final PropertyContainer propertyContainer) throws FrameworkException {
  
  		try {
  
  			if (securityContext.modifyAccessTime()) {
  
  				final Principal user = securityContext.getUser(false);
  				String modifiedById  = null;
  
  				if (user != null) {
  
  					if (user instanceof SuperUser) {
  
  						// "virtual" UUID of superuser
  						modifiedById = Principal.SUPERUSER_ID;
  
  					} else {
  
  						modifiedById = user.getUuid();
  					}
  
  					propertyContainer.setProperty(AbstractNode.lastModifiedBy.dbName(), modifiedById);
  				}
  
  				propertyContainer.setProperty(AbstractNode.lastModifiedDate.dbName(), System.currentTimeMillis());
  			}
  
  
  		} catch (Throwable t) {
  
  			// fail without throwing an exception here
  			logger.warn("", t);
  		}
  	}
docs: ----- private methods -----