Einstien had it right when he said that "time exist so that everything doesn't happen at once." That seems to be about the best explanation I've ever come across. And it fits with the dimensional nature of time; think of a timeline, it serves to separate and show the relationships between events.
This is a very complicated and contriversial subject. We may never have a definate answer because of the way our brains 'percieve' time. Some other creatures may be able to look at time the way we look at up and down. Their view of the universe would be vastly different then ours.
My proposition is this: We know that there are quantum fluxuations that create virtual particles. On the smallest scales, these particles must distort spacetime. Therefor there must be quantum effects on time. These effects may be what leads to time travel, FTL propulsion, teleportation, and any other 'spooky' effects that happen all the time on quantum scales, but so far have not been observed on the macro scale. I say give it time --- no pun intended ;-)