would be cool, but singleplayer campaign missions are often designed around time of day they need for that mission. Also, it would be really annoying if you could only play at night after you got home from work, and you never saw daytime in game.
That said, it would be neat to implement, just for fun. I’m guessing that you’d need to compile your own engine to create a way to access PC clock, unless UE4 already has functionality built-in. (Actually, is there already a BP node that does ?)