When I was a child, I wondered about eternity and time (I was a weird kid). And I would get frustrated because I could not logically come up with an answer to this: if God existed before time, going all the way back as far as one can go, with no beginning, how did He arrive at the point in time to begin creation? In other words, if there was no starting point, how would you arrive in the present? If the past is infinite, the present would never be arrived upon. My little brain could not comprehend this.
Matthew Henry, the famed theologian, has this comment:
“Should we ask why God made the world no sooner, we should but darken counsel by words without knowledge; for how could there be sooner or later in eternity? 
In eternity past, before time existed, there was no sooner or later! Our finite minds cannot comprehend this – it is a thought without knowledge, to paraphrase Mr. Henry.
It is arrogance to assume we can comprehend and wrestle to the ground the essence of time before the creation of it, when we ourselves are created in and limited by it. It is the essence of humility to admit that we lack the faculties to understand, but posses those necessary to appreciate, this incredible concept.
It should leave us in awe that our God is the One Who created us and the very time and space that we our bound too. He is above and beyond any limits that we can even comprehend – even the very existence of measured time.
 Matthew Henry, Matthew Henry’s Commentary on the Whole Bible: Complete and Unabridged in One Volume (Peabody: Hendrickson, 1994), 3.