I've been looking for a while at other threads, several have been close to what I need but not quite.
When a guest or customer sign up for our newsletter the field change_status_at populates with a timestamp.
However, if the guest or customer unsubscribe, we would like the the change_status_at field to pickup the current timestamp.
This is important to use because we do not use the newsletter "feature" of Magento 18.104.22.168 CE. Rather we export the newletter_subscriber list to a company to send an email.