$config_base_url is not set in config.php, so there is no address to build the link from.
Your schedule in the calendar you already use - on your phone, in Outlook, Google or Nextcloud - kept up to date as work is booked. It is a private link: anyone who has it can read what it shows, so keep it to yourself.
Made = escapeHtml(date('M j, Y', strtotime($feed['feed_created_at']))) ?> ·
= $feed['feed_accessed_at'] ? 'last fetched ' . escapeHtml(timeAgo($feed['feed_accessed_at'])) : 'not fetched by a calendar yet' ?>
Adding it to your calendar