"And it even tells the time!" - Day/Night Cycle on Compass UI

When Barrett hands you the compass for the first time (presumably after meeting you at Argos Mining and telling you to head to the Constellation headquarters), he says that it tells the time.

Well, how do you represent the time of day in a game where you visit lots of planets and moons? By showing the terminator line dividing day and night as it moves over the planet you're on. Pretty clever!