The first thing I would recommend is backing up the database. Go to File > Save as or File > Export, save the file to a safe place. After this procedure, reinstall the application. Since the product is not available anymore, the only thing you can do is to reinstall the product. By doing this you can get the guarantee that the setup will restore the database with the holidays. Secondly, check if the application supports Google Calendar. If it does, export the Google Calendar, then import it into the application.