The sky changes based on the sun - raise the sun to noon and the sky changes compared to lower the sun to or below the horizon. The angle of the sun makes a difference too, since the sky changes color near to the sun, and where that happens will depend on the angle of the sun.
You can have more than one sky and more than one sun, with each sun affecting a different sky, then you can turn those suns and skies on and off in LightMix, so you can set up your dawn, noon, afternoon shots in just one render.
Works fine here, would need to see an example of what you mean by it not working :)