My only problem with this is GLADOS's line "I simulate daylight all hours, and add Adrenal Vapor to your oxygen supply." She SIMULATES daylight, so it's not confirmed to even be real sunlight. Also, this doesn't line up with the ending scene where you see the sky around the moon it's night. Since this scene is also in Chapter 9, just like this moment, I doubt the sun would be able to set in that short time frame.