I imagine, depending on how open the scripting engine is, we could create a night/day system from scratch.
Yes, a few of us have implemented day/night cycles and NPC schedules in our prototyping and/or WIP. It requires a bit of 'fiddling' though and is not user friendly by any stretch of the imagination. The primary problem is that atmosphere triggers only fire when a player is moving inside of it. If a player just stands there, even if you update the atmosphere associated with the trigger, the atmosphere won't change. It introduces a bunch of unhappy workarounds that have to take into account numerous scenarios.
