Product needs update by button to show dates

Hello,
I am setting the sale price and dates of sale price with this code snippet:

$product = wc_get_product($post_id);
            
            if ( !is_wp_error( $product ) ) {
                $product->set_sale_price( $c->Price );
                $product->set_date_on_sale_from( date( 'Y-m-d 00:00:00', strtotime($c->FromDate)) );
                $product->set_date_on_sale_to( date( 'Y-m-d 23:59:59', strtotime($c->FinalDate)) );
            }
            
            $product->save();

But the problem is that timers are not showing unless I click the Update button in Woocommerce back end manually. Why is that?