According to Albert Einstein’s theory of general relativity, time is just another dimension in space, traversable in either direction, and our human perception of moments passing steadily and sequentially is all in our heads.
I agree — time is a belief, a mental construction. Widely believed, yes. True, no.
There is only now, now, now and all else is a mental story about what has happened, what is happening or appearing, and what will happen. Time is a mental construction that perpetuates the belief of being a separate and personal self.