Lord of ages

Athansius of course thinks the Arians are wrong because the Son is eternal.  But one of his more intriguing, and satisfying, arguments is based on the biblical notion that the Son is the one through whom the “ages” came into being (Hebrews 1:2).

Athanasius says, “every interval in the ages is measured [by Him], and of all the ages the Word is King and Maker, therefore no interval at all exists prior to Him.”

Since the Son is the measure of all intervals, the Lord of ages and bodies of time, there cannot be any “once” before He was.  How can there be an Arian “once” ( pote ) before the One who created all “onces”?

Pushing back a step: How can there be an “interval,” temporal or spatial, between Father and Son if the Son is the Lord of ages?