code: public void setDateLastModified(String resourcename, long dateLastModified, boolean recursive) throws CmsException {
  
          CmsResource resource = readResource(resourcename, CmsResourceFilter.IGNORE_EXPIRATION);
          getResourceType(resource).setDateLastModified(this, m_securityManager, resource, dateLastModified, recursive);
      }
docs: Changes the "last modified" time stamp of a resource.<p>
  
  @param resourcename the name of the resource to change (full current site relative path)
  @param dateLastModified time stamp the new time stamp of the changed resource
  @param recursive if this operation is to be applied recursively to all resources in a folder
  
  @throws CmsException if something goes wrong