If you see the error below:
it is most likely that your MySQL collation is not utf8. To do this you need to make sure that you set your database to utf8 and you can do that via phpmyadmin found on your hosting provider's cPanel application.
1. Once you are in your phpmyadmin application, browse to the Database that your current Concrete5 installation is using. In this example we installed our Concrete5 on devjdyn5_6868a.
Once you are in your Database go to Operations menu and look for the Collation section. If it is set to latin1_general_ci make sure to change it to uft8_general_ci. That way you are allowing your Database to accept Unicode characters. However, if you already have encountered the error above chances are if you reinstall the Calendar Pro add-on it will not resolve the anything yet. So the proper way of doing it is to Uninstall the add-on first then delete the tables associated with this add-on namely:
Once, you have removed the tables you can now reinstall the Calendar Pro add-on and the MySQL error should be gone this time.