The future and the past are purely conceptual. Everything in the past is gone; everything in the future is yet to be. The former exists only in memory; the latter only in imagination. Only the current instant actually exists.
Yet it appears that one instant clearly influences the next. If you are currently sitting in a chair, it is far more likely that in the next instant you will still be there, or at least in the same room, rather than standing on the moon.
How can the current instant affect the next (future) instant if they don’t exist at the same time? What does it even mean for two instants to "exist at the same time?"