News that would spark the uprising against the Combine has yet to reach the ears of the denizens of earth. The one man who holds this knowledge now finds himself hunted by the Combine in order to prevent this news from spreading.
Showing the different soundscapes used for morning and evening.
Nice, feels like I'm really there!
Wow, good job,guys!
Hmm, are you planing an actual day/night circle of sorts?
The time changes as you progress through maps, just like in HL2. Source isn't capable of a true day/night cycle. In the case of this area, the player passes through it at a later date, hence the time change.