使用ACF插件提供的“get_field”函数获取“date” meta字段的值。它还使用“DateTime”类获取当前日期和时间，并从事件日期中减去24小时以获得截止日期和时间。然后它将当前日期和时间与截止日期和时间进行比较，并设置“purchasable”如果当前日期和时间大于或等于截止日期和时间，则状态为false。
把下面的代码放到主题的functions.php中

add_filter( 'woocommerce_product_is_purchasable', 'my_custom_is_purchasable', 10, 2 );
function my_custom_is_purchasable( $purchasable, $product ) {
    // Get the value of the "date" meta field
    $event_date = get_field('date', $product->get_id());
    // Get the current date and time
    $current_datetime = new DateTime();
    // Get the date and time 24 hours before the event
    $cutoff_datetime = new DateTime($event_date);
    $cutoff_datetime->sub(new DateInterval('PT24H'));
    // Compare the current date and time with the cutoff date and time
    if($current_datetime >= $cutoff_datetime){
        $purchasable = false;
    }
    return $purchasable;
}

我想明白了，下面是适合我的代码：

function unpublish_24h_before() {
// Get all products
$args = array(
    'post_type' => 'product',
    'post_status' => 'publish',
    'posts_per_page' => -1
);
$products = get_posts( $args );

// Check expiration date for each product
foreach ( $products as $product ) {
    $expiration_date = get_field( 'date', $product->ID );
    if ( !empty( $expiration_date ) ) {
        $expiration_date = strtotime( $expiration_date );
        $time_left = $expiration_date - time();
        if ( $time_left <= 24 * 60 * 60 ) {
            // Move the product to the trash
            $product->post_status = 'draft';
        wp_update_post( $product );
        }
    }
}} unpublish_24h_before();