Has anyone worked out what the different modes in settings do? There's Auto, Day & Night but all the instructions seem to say is that "you can choose which mode to use" without actually explaining what the difference is!
I have no knowledgable answer (my varia tail light is in shipment - for eventual pairing with my 810). However, I would think it is in reference to how the head unit reacts to a vehicle alert. It would make sense to turn on the backlight during night time when a vehicle is detected. If Night mode is selected, then the backlight always comes on. If Day, then it never comes on. And, Auto would turn on the backlight based upon the sunrise/sunset tables for your GPS location.
Then again, I could be completely off base.
Doug.