OK, this time the upgrade to 17.1 worked, the Zorin dev team (again) did a great job. All I had to do was to install gnome-shell-extension-manager via apt and I was able to add the year 
Thanks to all 
OK, this time the upgrade to 17.1 worked, the Zorin dev team (again) did a great job. All I had to do was to install gnome-shell-extension-manager via apt and I was able to add the year
Thanks to all