Look there's a signpost ahead. Your entering... the Twilight Zone. The first person who can answer this with some reality based information vs. quantum theory gets... my everlasting respect? A cookie? Hell, give me your PayPal and I'll send you what I can, but I seriously hate mystery functions, and worse functions or features that either make zero sense or plain do not work in any understandable way.

Now that I got the preamble out of the way, how about I get to what I am blathering on about, what say? The item I am referring to is the "Twilight" screen brightness/color setting on the X350 touchscreen. There's folks on here that have (very) differing perspectives, experience and knowledge. Perhaps we can put our combined knowledge together and figure this one out. Over 6 years and two of these cars, I have never experience "Twilight" doing anything other than "Night" setting for the touchscreen Brightness/Contrast Settings. Perhaps it was not programmed as intended, but to my thinking it (twilight) would be for dusk/dawn periods where its not quite night, nor is it day - neither fish nor fowl, shall we say? Actually we don't have to say that. But we CAN say that it matches night in every way, and I have experimented with combinations of headlights on/off, parking lights on/off and setting it different to night and day, and yet it always matches NIGHT.

I would expect it to keep the screen bright when the ambient light sensor on top of the dashboard detects enough light, but the driver has flipped the lights on. OR... It would follow the "Auto" settings of the lights in some different way.

So what is the consensus. I don't object to theories on it's intended function, but what I would really be impressive is someone illustrating it DOING some function other than night. ANYTHING different would be nice... The one theory I will not get behind is it's "just a third option but generally follows night settings. That's not a third anything.

https://play.google.com/music/m/Tf5l...Golden_Earring

 

I tend to regard 'Twilight' as simply an alternative for night use rather than as some form of intermediate state; ie a dimmed version of 'Day' if you prefer a light background with dark markings, rather than the black background with bright markings (an inverted, 'negative', version of 'Day') that 'Night' gives you. Personally I prefer 'Twilight' to 'Night' when it's dark.

I think 'Day', 'Night-Positive', and 'Night-Negative' might be better names.

As far as I've determined it's purely a manual option; 'Auto' only seems to switch between 'Day' and 'Night'.

I think 'Twilight' makes more sense if you're using Voice Control; it's one of the few VC commands that I actually use. ('Display Off' is my favourite).

 

Partick, That has me motivated to get a replacement VACM. The one I installed a few years ago works, but from what I understand, the car it came from may have had different equipment. It is missing all features that refer to the screen. I was really annoyed. Even the training covers the screen items yet they are not there, not even in help. I will have to hunt down another module. I don't see as many around lately.

 

The only thing I've seen it do is stay on "day" when wipers are on auto.
Mode :Lights on auto
Mode: Wipers on auto
When it rains during the day, wipers come on, headlights come on, and screen stays on "day".
I have never noticed the inverted color screen as Partick mentioned, but now I have to check tomorrow. Makes sense, just like and Iphone at night.
How is it that we have been driving these cars for so many years, diving into the deepest issues that the manufacture has never dared to go, and yet we can't figure out the screen. One of the engineers for the X350 is somewhere laughing his A*& off at us.

 

Looking at mine the inverted colours for 'Night' only seem to apply to the Navigation/SatNav screen. Other screens, eg Audio, seem to have no difference between 'Twilight' and 'Night'.

 

The Cat is an evolutionary beast, and I am convinced the Twilight is non-functional, just like your appendix. It is a leftover from when cats had to hunt at dusk.
Or...I think it is there to distract your attention from all the other things that sometimes don't work.

In the Brightness/Contrast screen, one can press Day and set that brightness, then press Night and set that brightness independently.
However, whatever one sets with Night pressed is also what is seen with Twilight pressed (and vice-versa).
If Night and Twilight cannot be independently set, then it's non-functional! (...says I. My PayPal details are in the post)

Tested on X358. which I'm sure is the same as later X350.

What I can say, is that if you pull over in twilight to read the navigation manual (JJM18 05 32 801) all 73 pages, then you won't find any mention of twilight and this mysterious twilight will be over anyway.
(It is mentioned in the 350 page Owners Handbook (JJM 10 02 21 802), but nothing useful and by then a few moons of twilight will have passed anyway)