An increase in entropy signals what we have defined as the "positive" time direction, but physics may never tell us why humans can only seem to experience time towards the positive direction

I think I read a good explanation somewhere. We experience time by forming memories. If our molecules somehow participated in times still future to us but no memories were formed, we would not be aware of it. And the formation of memory (in the brain, or in any mechanical recording system) is a creative process, which because of that famous law can only reliably happen when energy is consumed and entropy increases. Given that memories can only form in the "positive" direction, we are obligated to experience time that way.

In my view, the psychology of perception is more complex and mysterious than the physics (not to say that I have mastered either). Evidence of variable perception of time is hard to come by. Experimenters concluded that "frightening events are associated with richer and denser memories ... And the more memory you have of an event, the longer you believe it took." This, I think, is the key to resisting the common perception of time accelerating with aging: avoid getting stuck in repetitive behaviors, seek novelty and adventure. Buy experiences and not material goods.

I remember a bizarre time perception I once experienced. I had listened to a Radiolab episode about Ötzi while biking to the train station, then started reading the Wikipedia article on the train. The podcast was quite affecting, and I felt an uncanny connection to a man so remote in time and space. Then, with perfect timing, Pandora began playing "Beyond This Moment". I was about a quarter through the article, and sensed that I would still be reading it when the song finished. I felt like I was aware of the whole of that time at once, as if the little slice of time called the present had expanded to several minutes, and I was already enjoying the memory of the beautiful experience I was about to have.