Tracking Time
Time in the world works just like time in the real world (duh). But unlike the real world, we have very fine control over speed in this simulation, which means it can get difficult to track time if we don't have a measure of it.
Daylight is a function of space and time on the world map. Light values constantly shift from 0 to 1 as shown in this sped up gif. In the dark, agents cannot see (unless Moonlight is enabled), and in the daytime, they can see each other and they see a grey color everywhere else they look. The agents are free to run in the dark if they like; there's no other penalties for darkness or bonuses for light.
50 days count out an Epoch, which is the main measure of time once the simulation gets going. Nothing interesting happens in Epoch 0, or the first 50 days. Typically you have to enable Fast Mode to see anything interesting develop.
Once counting Epochs, the simulation doesn't stop. But it does reset the day counter. Together with the Epoch, the Day, and a hidden variable known as Modcounter, every agent's Clock inputs keep perfect resonance even when the epoch rolls over. Reports show the epoch and day number also, to help visualize and control data in spreadsheeting.