Problem
Lighting is the part of a 3D scene that's hardest to fake convincingly—a static day scene and a static night scene are two separate art problems. Animating the transition between them is a third, harder one.
Approach
The sky shifts through day, sunset, and night on a loop, with shadows sweeping across the ground
as the sun moves and a moon taking over once it sets. Fireflies fade in after dark as a particle
system. A lil-gui panel exposes the cycle speed and lighting parameters live, which is what
turned this from "does it work" into "does it look right."
What I'd change
The cycle is time-based, not tied to any real clock or season—a version that actually read the viewer's local time would be a small change with a genuinely interesting payoff.