I have an 08 G35 and I have the auto setting. I guess at some point they did carry it over to the G35's

 

Perhaps; however my 2004 G35 Coupe worked as I described above. But I still believe that these day/night mode questions come up because the owner doesn’t understand that, by design, setting the dash lighting rheostat beyond a certain limit results in the day mode being on all the time.

It's a useful function in that in California we now have to turn on our headlights during the day when it's raining and the wipers are on. I find that the dash lights then go into night mode and are often too dim for daytime use. Turning the instrument brightness control switch on my G37 to full brighness turns daylight mode back on. Of course, in this case I have to manually turn it back when it's nighttime again.