This is a surprisingly often misunderstood point. Even scholars assign dates to different aspects of the Veda. To ask how old the Veda is would be the same as asking how old nature is. The Veda is nature. It is eternal. The dates given to different aspects of the Veda are only historical records of when it was first recognized. I say recognized instead of cognized because the Veda was cognized far earlier than recorded history recognized it. The Veda is not a book or chant someone made up. The Veda is nature.