P.209 - §4 The Ancients of Days are all basically identical; they disclose the combined character and unified nature of the Trinity. They possess individuality and are in personality diverse, but they do not differ from each other as do the Seven Master Spirits. They provide the uniform directorship of the otherwise differing seven superuniverses, each of which is a distinct, segregated, and unique creation. The Seven Master Spirits are unlike in nature and attributes, but the Ancients of Days, the personal rulers of the superuniverses, are all uniform and superperfect offspring of the Paradise Trinity.
P.209 - §6 The Ancients of Days were all trinitized at the same time. They represent the beginning of the personality records of the universe of universes, hence their name--Ancients of Days. When you reach Paradise and search the written records of the beginning of things, you will find that the first entry appearing in the personality section is the recital of the trinitization of these twenty-one Ancients of Days.