Two threads in less than five minutes. Anyway.
Back in the days, I had wanted to use this idea in one campaign or another, but - well, we all know how I ended up.
Basically, the idea was to have a paranormal detective investigating a crime in three different periods of time - past, present, and future. Whenever this detective would summon another time, the environment would change, to allow him or her to see things that otherwise are not (or no longer) there. As an example: in the present, there's a Monastery, in the future, there's a Barracks, and in the past, there's nothing at all. This would require three different, yet nearly identical landscapes, or so I figure - and a whole lot of triggers and AI cross-communicating... But hey, that's the standard nowadays.
I figure there's probably someone who thinks this is a good idea, and if not - well, no losses on my side. Enjoy.