The two titles "Ancient of Days" and "Head of Days" are clearly referring to the same white-haired object and it is very intriguing who this "son of man" is meant to be. Was it a past event or imagined future one?
The names though are quite different. It is my opinion that the Book of the Zohar provides the missing clues. "Days" is "Seas" (Yomin), i.e. vessels, whereas "Ancient" (Otiq) means "removable". "Head", used in the Enoch version, pretty much means just that - a head.
The writers are showing that they are in possession of secrets known only to a certain few, presumably to increase its status and credibility.
Head of Days... רֹאשׁ. Also means the Leader, the head, the keter.... the crown on the head of the Bar Enosh... the Son of Man.... Yeshu ha Notzri
הכתר על הראש הוא ראש ימים וימים קדומים של ישו הוא בן האנוש
Yes... if you can read Hebrew and Aramaic the identity of Bar Enosh, Son of Man becomes clear.