[DGD] time travel

[Shentino]

Me and bct were having an interesting discussion about time travel in a mud.

Some issues:

1.  Rollback or replay of a character's past or present (especialy that of a
PC), if there was a significant change in the past that owuld also affect
the present

2.  All the wonderful things of causality.

It might be kinda fun, but how does one track this stuff?  And how to make
it interesting?

I'm talking perhaps more than just chrono-trigger style "time-based
geography" separated by millenia, but treating time as a fluid continuum.