For any of y'all out there who share my little obsession with continuity and such, here's an example of the Marvel Universe floating timeline in action.
Captain America was a WWII superhero who was then revived in the Silver Age of comics in the 1960s. The idea was that he'd been preserved for a couple of decades in a block of ice, enabling him to appear in stories that were then contemporary.
But Marvel uses this floating timeline thing, which requires it to retcon events - sometimes silently, sometimes explicitly. Marvel is currently operating on the basis that the key initiating events within its main "616" continuity - those of Fantastic Four # 1, when Reed Richards and his team first journeyed into space - happened 13 years ago. That means all the other early events of the Silver Age must (for the moment) be thought of as happening in about, say, 1998. If Marvel maintains the gap at 13 years, to keep its characters relatively young, the starting date will keep changing.
It seems that they're now talking about Captain America being in suspended animation for half a century (it should be about, hmm, 53 at this stage, shouldn't it? But who's counting when you need to keep a floating timeline going?) and having fresh memories of 60 years ago.
I'm not actually so interested as to go out and buy this Captain America mini-series about how he copes with waking up in our day, but presumably the events will be depicted rather differently from what Marvel did back in the '60s.