This post is another attempt to go over the same ground in a back post.
You are in pain, and then the pain ends. You exclaim: "Thank goodness the pain is over!" It is thought by some A-theorists (who think that there is an objective division between past, present and future) that B-theorists (who do not think there is an objective present and who think temporal determinations are relative) can make sense of the sentiment. After all, the sentiment is not a relative one. One is not exclaiming: "Thank goodness that the pain is later than this remark!" Rather, one is being grateful (implicitly to Providence?) that all the pain is, objectively, in the past.
But if time travel is conceivable, this is mistaken. Suppose I travel to the year 2200, and find myself with a horrendous headache. I decide to go back to 2008. Simultaneously with my return to 2008, my pain coincidentally goes away. I exclaim: "Thank goodness the pain is over!" This exclamation makes perfect sense. But if it does, then the A-theorist is wrong to think that the exclamation is an expression of joy at all the pain being in the objective past. For the pain is actually objectively in the future: the pain is 2200. But it makes no sense to dread that objectively future pain. For that objectively future pain is not in one's subjective future. It is in one's subjective past. Therefore, in the exclamation "Thank goodness the pain is over!" the word "over" refers to subjective time.
But subjective time is not the time that the A-theorist talks about. For instance, if there is time travel, then there may be no objective fact about what subjective time it is for some person x. For this person may now be twice-over present at the same time, having traveled back to this time, and so there are now two subjective nows for that person.
I am growing more and more convinced that subjective time, or more generally internal time (subjective time is only had by conscious substances; internal time can be had by non-conscious entities) is the logically primitive form of time. In those possible worlds where the internal times are appropriately correlated with causation, there is also external time—the time of the world—which supervenes on, and even reduces to, internal time. And both internal and external time is B-theoretic in nature.