I have a stock reduction script that works perfectly. The only problem is, when a purchase is made and the stock is reduced, the date_modified meta is updated. This causes problems for other scripts I have, as the post isn’t actually updated – just the stock.

How can I achieve the same result with this code, without it actually updating the date_modified meta? (ie: only update date_modified when the product itself is manually updated).

// ---------------------------------------------------------------------------------------- //
// --------------------------  REDUCE WEIGHT BASED ON WEIGHT FIELD  ----------------------- //
// ---------------------------------------------------------------------------------------- //

// reduce stock based on 'pa_weight' attribute
add_filter( 'woocommerce_order_item_quantity', 'filter_order_item_quantity', 10, 3 ); 
function filter_order_item_quantity( $quantity, $order, $item )  
{
    $product   = $item->get_product();
    $term_name = $product->get_attribute('pa_weight');

    // 'pa_weight' - keep only the numbers
    $quantity = preg_replace('/[^0-9.]+/', '', $term_name);

    // new quantity
    if( is_numeric ( $quantity ) && $quantity != 0 )
        $quantity *= $quantity;

    return $quantity;
}


/**
 * Order change stock reduction fix.
 * 
 * @param $prevent
 * @param $item
 * @param $item_quantity
 * @return bool|mixed
 */
function custom_stock_reduction_order_change( $prevent, $item, $item_quantity ) {
    $stock_reduced   = wc_stock_amount( $item->get_meta( '_reduced_stock', true ) );
    $stock_reduction = filter_order_item_quantity( $item->get_quantity(), null, $item );

    if ( $stock_reduction == $stock_reduced ) {
        $prevent = true;
    }

    return $prevent;
}
add_filter( 'woocommerce_prevent_adjust_line_item_product_stock', 'custom_stock_reduction_order_change', 10, 3 );