Help about a stage in real-time?

I'm sure I'll regret asking this question but anyway...

I'm making a very simplistic stage - it's urban, in open-air, with an advertising clock and streetlamps.

It's (for lack of a better word) in real-time - the clock works and follows an independent time, the sky changes from day to night and vice versa, and the poles flash on and off when they need to.

Making this scenario is easy, just convert the times and synchronize everything in the animations. And here comes my question.

In this method the programming forces the scenario to always start at a fixed time and I want it to be random, that every time anybody play in the scenario it always starts at a different time.

Is there any way to do what I want?

Ps: the only idea I've had to do this is to put arithmetic expressions and variables, things that always show up in character programming but that I've never seen in stages - it is possible to put this in a stage.def?

You must look for a mugen Background controllers tutorial.

I remember a Final Figth based stage wich indeed go from dusk till dawn & visceversa. Look for it and chack the BGctrl in the def.