The universe could be 13.5 BY old, 35 BY old, or 3.5 BYo, it may in fact be timeless with no beginning or end. I don't know, and that's OK. In the mean time, we are stuck, for the most part, using our assumptions on the accuracy of these dating methods, regardless of how inaccurate they may be.-I thought the Earth's age was determined by uranium dating.