I once asked a similar question but didn't really get the answer or discussion that I was looking for and decided to start clean. Recall that in Galilean (classical) spacetimes its assumed that space-time itself gives rise to some way of defining or giving sense to what it means for distant objects to be present or absolutely simultaneous. In special relativity the spacetime structure lacks this feature so its not the case that there is an objective absolute present in Minkowski spacetime. This is all fairly interesting if we were assuming spacetime is even a real thing. How do relationists (anti-realists) to space and time define or even approach making sense of absolute simultaneity? If a relationist wanted a form of absolute simultaneity how would it or how has it been defined in the literature? Can a relationist be committed to neither a presentist or enternalist position on the ontology of time? Because relationist may not have spacetime structure or material properties to ascribe a complete sense of absolute simultaneity to every existent object but clearly a relationist to time also doesn't think the future or past exists in an eternalist sense. Could you be in the middle ground or a mixture of presentism/eternalism?