Anyone who stops and really thinks about our commonsensical notions of time can instantly see that the idea is a troublesome one, that out instinctive sense of it as a directional river is fraught with logical inconsistencies that simply don’t appear to us in our everyday sensations.
The Einsteinean revelation that time is not absolute was the first hint that all was not as it seemed with this most instinctive of concepts, and there is some thrilling recent theoretical work that proposes alternative explanations for entropic progression that do not demand the existence of linear time.
Of all counter-intuitive realities, few are harder to swallow - but so many philosophical problems and paradoxes are smoothed away by it.
Time does not exist, just as Plato always said.
That time in fact makes no sense at all is easily shown by the fact that the notion of it beginning is seemingly as absurd as the notion of it not beginning.
It is a logical commonplace that temporal infinity is impossible, because it would mean that the past stretches as far back as the future stretches ahead, thus 'now' can never have occurred, and you and I could never have been born. But the idea of time starting somewhere is equally absurd because it posits the very thing it prohibits - a time before time.
What this profound mystery really tells us, I suspect, is something not mysterious at all, but perhaps a little deflating to the ego.
What I think we have here is a problem of brains, not of reality. Our brains evolved for various mundane Darwinian reasons, and the ability to ponder the mystery of time is presumably an accidental bonus of selection for some other feature. There is no reason to think our brains are capable of grasping everything: here, I think, is an example of where our brains end as reasoning machines; trying to grapple with the problem feels like the brain banging against the inside of the skull.
What does the non-existence of time mean for determinism?
It makes it fundamentally less mysterious, and also less occult. It robs the term of any unwanted connotations of fate and predestination; there ceases to be anything predictive about it because there is no longer any future for it to predict: a better name than 'determinism', therefore, might be 'concurrence'.
According to the most persuasive theories I have read, the illusion of linear progress is caused not by sequentialism but by consciousness's 'choice' of existent states, for not only do all perceived 'moments' of time (the supposed past, present and future) exist simultaneously, but so too do all possible moments.
So our 'futures' are 'determined', but from an infinite choice of possibilities, with various causal factors influencing the selection. This is neither quite determinism as it is intuitively defined, nor free will as it is intuitively defined. It is both, and neither.
It is, I think, the true model of Dasein.