Add LasT Edited Column TO CPT

//http://andrewnorcross.com/tutorials/modified-date-display/
add_action ( 'manage_posts_custom_column',	'rkv_heirch_columns',	10,	2	);
add_filter ( 'manage_edit-stellenangebot_columns',	'rkv_page_columns'				);

function rkv_heirch_columns( $column, $post_id ) {

	switch ( $column ) {

		case 'modified':
			$m_orig		= get_post_field( 'post_modified', $post_id, 'raw' );
			$m_stamp	= strtotime( $m_orig );
			//		$modified	= date('n/j/y @ g:i a', $m_stamp );
			$modified   = date(get_option( 'date_format' )." @ ".get_option( 'time_format' ), $m_stamp );

			$modr_id	= get_post_meta( $post_id, '_edit_last', true );
			$auth_id	= get_post_field( 'post_author', $post_id, 'raw' );
			$user_id	= !empty( $modr_id ) ? $modr_id : $auth_id;
			$user_info	= get_userdata( $user_id );

			echo '<p class="mod-date">';
			echo '<em>'.$modified.'</em><br />';
			echo 'von <strong>'.$user_info->display_name.'<strong>';
			echo '</p>';

			break;

			// end all case breaks
	}

}

function last_modified_column_register_sortable( $columns ) {
	$columns["modified"] = "last_modified";
	return $columns;
}
add_filter( "manage_edit-stellenangebot_sortable_columns", "last_modified_column_register_sortable" );
add_filter( "manage_edit-stellenangebot_sortable_columns", "last_modified_column_register_sortable" );

function rkv_page_columns( $columns ) {
	$columns['modified']	= 'Letzte Bearbeitung';
	return $columns;
}