Vacation Robo-Post, Lost Discussion Group Edition: Where (and When) Is the Island?

So a while back I was noodling on the idea of just what had gone on on the Island in between the Oceanic 6's rescue and Jeremy Bentham's return to the mainland. More specifically, I was wondering how much could have happened in the space of—what was it, three years?—and how the writers could compress all that story in however much flashback time they'll have available. After all, they covered only 100 Island days and change in four seasons.

And then I had a flash: who says it's been three years? Who says the Island only moved in space? Who says it moved in space at all? What if it moved... in time?

Ooooh, I thought this was an awesome theory! Ooooh, I was proud of myself! Then I googled it and discovered that Maureen Ryan, as well as half the Internet, had the same theory shortly after the finale aired. And also, Tom Shaw posted it right here. But I'm going to try to pretend I don't know about any of that.

Regardless, whether the Island moved in time or space, knowing what we know about Lost, I think it's a fair guess that (1) the location, geographic or temporal, that the Island moved to is not merely random and (2) it will probably be something really cool.

So let's take that as your LDG question of the day: Where did the Island go? When did it go? And why does it matter?