Don't know about Australia, but in Texas it doesn't get dark in the winter by 4:45 PM.
Could be, but it could also control the overhead lights on the floor.
I agree.
Not that I don't believe you, but do you have a source for Ruby & Oswald being filmed in the actual TSBD?

That makes sense. Lights on the floors near the stairways illuminating the stairways.
Don't know about Australia, but in Texas it doesn't get dark in the winter by 4:45 PM.
I didn't mean "a dark overcast day" to mean night, the sun doesn't go down at 4:45 in Australia either but at that time in the winter on a cloudy overcast day it's get dark. I just had a quick check and on the earliest sunset time you are about half an hour behind which under those conditions described above is insignificant.
Could be, but it could also control the overhead lights on the floor.
That's what I meant. But thinking about it, at night when you switch off this light then what do you do, there must be some sort of soft lighting at the elevator or stairs?
Not that I don't believe you, but do you have a source for Ruby & Oswald being filmed in the actual TSBD?
The only source for filming location I could find was on IMBD "Filming Locations: Dallas, Texas, USA"
Btw did you see my comparisons a page or two back that is pretty definitive, finding locations with that level of accuracy very rarely if ever happens. Other locations like the Texas theater and the Paines and Fraziers houses are very obviously different but the Depository and the Rooming house are filmed on location.
Anyway here's some more frameshots of the back of the building and the 6th floor.


And this gif should put any guessing to bed, through the sniper's nest window in the TVmovie we see the same 3 buildings beyond that actually exist there.

That makes sense. Lights on the floors near the stairways illuminating the stairways.
Yes, but I still reckon that they needed a light halfway down the stairs to illuminate the bottom section that leads to a possible closed door.
JohnM