/**
 * Add edited date column on product page (header)
 */
function add_edited_date_product_column_header( $columns ) {	
    //add column header
    $columns['edited_date'] = __( 'Last Modified', 'woocommerce' );

    return $columns;
}
add_filter( 'manage_edit-product_columns', 'add_edited_date_product_column_header', 10, 1 );

/**
 * Add edited date column on product page (content)
 */
function add_edited_date_product_column_content( $column, $postid ) {
    // add column content
    if ( $column == 'edited_date' ) {	
        // Get product object
        $product = wc_get_product( $postid );
		
        // Get product date modified
        $date_modified = $product->get_date_modified();
		
      
		
		 $modified_date   = the_modified_date( 'Y/m/d - g:i A' );
  $modified_author = get_the_modified_author();

  echo $modified_date;
  echo '<br>';
  echo '<strong>' . $modified_author . '</strong>';
    }
}
add_action( 'manage_product_posts_custom_column', 'add_edited_date_product_column_content', 10, 2 );

/**
 * Make the edited date column on the product page sortable
 */
function edited_date_product_column_sortable( $columns ) {
    $columns['edited_date'] = 'edited_date';	

    //To make a column 'un-sortable' remove it from the array
    //unset($columns['date']);
	
    return $columns;
}
add_filter( 'manage_edit-product_sortable_columns', 'edited_date_product_column_sortable', 10, 1 );

/**
 * Orderby edited_date (product)
 */
function edited_date_product_column_orderby( $query ) {
    if( ! is_admin() )
        return;

    $orderby = $query->get('orderby');

    // edited date, product
    if( $orderby == 'edited_date' ) {
        //$query->set( 'orderby', '' );
    }
}
add_action( 'pre_get_posts', 'edited_date_product_column_orderby' );