$post_date = get_the_date('Y-m-d', $product->get_id());
$post_date_time = strtotime($post_date);
$current_date_time = strtotime(current_time('Y-m-d'));
$date_diff = ($current_date_time - $post_date_time) / (60 60 24);
if ($date_diff <= 30): ?>
<span class="new-label">New</span>
<?php endif; ?>