The first plan said no day and night. I wanted the sim small, and a clock felt like decoration. This week I put one in, and I think it’s the least decorative thing I’ve added so far.
A short day
The city keeps its own time. A full day, from one dawn to the next, is half a real day, and it runs whether you’re logged in or not. Because the game day is short, night comes twice in every real day, so it isn’t something that only happens to people in one timezone.

Night does one thing: it takes away how far you can see. The circle around your character shrinks to about half. In daylight you can spot a zombie a good way down the street and decide what to do about it. At night it is close before you see it. Nothing else changes. The zombies are the same zombies, in the same numbers, moving at the same speed.

I didn’t want a night that makes zombies faster or angrier, because then night is a difficulty setting. I wanted a night that changes what you rely on. The sound log matters more at night than at any other time, because it is often the only warning you get. A groan from the east and nothing on the screen means something is out there behind a wall, and you get to decide whether that’s close enough to care about. The hearing entry put a log of noises at the centre of the game; night is when that log is most of what you have.
What night does to the rest
A building is worth more at night, because inside you’re not the one with the small circle anymore. A gun is worth less, or costs more, because a shot in the dark tells everyone exactly where you are and you can’t see who heard it. A trip you’d make without thinking at noon is one you plan at midnight.
The colours follow the clock. Midday is clear, dusk and dawn go warm, night goes deep blue. On a map that is still just coloured squares it’s the first thing that makes the city feel like it has weather.
Night arrives in the middle of a trip whether you planned for it or not, and a player who set out at dusk with a full bar is going to find the walk home very different from the walk out.