If you do see an error saying “Date improperly formatted, correct in Dashboard” within your rich reviews page, it is because you have to correctly input the correct date in a review if it is missing or set to: 0000-00-00 00:00:00
This will need to be changed to a correct date format in the back end of the Rich Reviews editor when you logon to your wordpress site.
To fix this go to Reviews > Approved Reviews > Click on the reviews that have 0000-00-00 00:00:00 set as the default date and time. Set this to the correct time manually. (it is supposed to automatically update when you add the new review) Click submit review at the bottom when done to save. The error for that review will go away.
Upon further investigation and trying to get support from the plugin authors, it appears this plugin is no longer available for download due to security issues. It must therefore be uninstalled and replaced with a know working and supported wordpress reviews plugins.
Here is an alternative plugin to try which appears to have a lot of installs and support. WP Customer Reviews