Lock an Application

How can I lock down an Advanced Template application so it cannot be used after a certain date?

In /frontend/config/main-local.php:

$config = [
    // ...
    'catchAll' => time() > strtotime('2019-02-20 00:00:00')
        ? ['site/offline-notice']
        : null,
    // ...
];

Worked beautifully. Thank you.