Time, as we know it, is a man-made concept. Invented in order to help explain, and understand the universe.
We perceive time to be moving in one direction only, forwards. It has however been theorised that what we perceive as the only way time can move is incorrect. Go back far enough, the "Big Bang" and time expanded both ways, only we can't see those for whom time is travelling in "reverse" by our understanding. Nor can they see us.
Just think, somewhere out there, there's another you getting younger, with all the joys of youth to look forward to.