If we're going to accept that the island really has moved, (which we kinda have to since we saw it disappear), then it has to be that the people on the island aren't just skipping through time, but space as well. I think it's weird that they never talk about this, since they seem to have a pseudo-science reasoning for everything else.
Come to think of it, time travel in any sci-fi story doesn't really make sense without travel through space since the earth is always moving. Your position on the earth isn't really a good absolute reference point.
All rambling aside: time travel makes no sense whichever way you look at it. I should get over this and move on. So far I think Lost has done a good job with the pseudo-science of time travel. I especially enjoyed how they sidestepped the causality paradox with Faraday's "If it didn't happen, it can't happen." I'm just waiting for their space jump explanation.
