Just like you can schedule publication of content you can also schedule the expiration of an object. This is available under the Action button of any content object so long as the user has rights to history for an object.
This is often used in combination with scheduling publication, so that you may schedule an object to be published on a future date, stay live for a few days, then expire back to the previous version. For example, you may want to post a special message that only lasts 24 hours on your web site. You could schedule it to be published at any date, and then schedule the expiration of that object for exactly 24 hours later. The content will revert back to the previous version, exactly the same way it would had you selected History and clicked on the last version of content. An email will be sent to the address specified once the expiration has been performed.
Note that this will only go back one version of the content.