Spacetime is a mathematical abstraction which represents the totality of matter, energy, and space which exists potentially. It is important to realize that matter, energy and space exist concretely only while they are "contained" or "embedded" within a "present moment" (i.e., within "conscious experience").
Let us suppose that two minds observe the matter and energy associated with a given spacetime point or "slice" (let us say the "slice": October 1, 1500 AD). A question immediately arises: when do these two "observations"/"experiences" occur in relation to one another? In other words, what is the temporal relation or sequence of these two "experiences"/"events"? The answer of course is that there is no temporal relation between them. (See my article, "Temporal Passage, Causality, and the Mind/Body Problem".)
I have argued in other essays that temporal conflicts or inconsistencies cannot arise between two experiences of reality. I believe this conclusion has implications for time travel: it seems to suggest that self-consistent, geometric "time travel" scenarios are possible.