[danfo]

There are benefits to dark UI for dim environments. The fad that I too am sure will pass is using a jarring UI for the environment just because it is cool.

There are fundamental differences when designing for bright/day vs dim/night that benefits humans. In-car GPS was a specialised UI that paid attention to this earlier than our computers. The night UI maximised clarity in a low-light environment without being distracting. The day UI met the daylight with similar clarity. Never jarring.

Triggering a system-wide change across devices when the sun dips below the horizon is a nice start. The fact that it trickles even as far as webpage and VS Code theme is just awesome stuff.

Speaking to your detrimental cases, maybe the auto-change could be based on ambient light level rather than sunset time. It is certainly possible. Excluding the Nordics, the better solution is likely to move humans closer to natural light. Dim the room or build for natural light, rather than our screens able to be brighter to meet an artificial environment.