* cache or it is empty
*
* @param string $owner_nick Nickname of the feed owner
- * @param string $last_update Date of the last update
+ * @param string $last_update Date of the last update (in "Y-m-d H:i:s" format)
* @param integer $max_items Number of maximum items to fetch
* @param string $filter Feed items filter (activity, posts or comments)
* @param boolean $nocache Wether to bypass caching