Your website likely already has a solution for prompting for cookie and other policy acceptance to meet GDPR requirements. This solution likely tracks policy acceptance and cookie consent with a custom cookie.
The DNN software uses a very limited number of cookies for its core functionality, both to minimize the overhead imposed by the platform and to avoid consent issues that developers cannot mitigate. As such, most custom cookies and their associated consent notifications need to be implemented by developers to meet specific needs.
If you are already using a third-party consent module from the DNN Store, there should be tools to version and retire cookies that relate to older versions of your policies. If not, you should contact the module developer to see if that functionality can be implemented.
If you are using a custom-coded solution, you can retire the cookie used to track the acceptance of the previous version of your policies and implement a new one to track the current version. When you implement the new policy, update your site code on that date to both write and check the new cookie. The old cookie will expire on its own.