the notion that there's such a place as 'outside spacetime' and that Yahweh is there.
I am not sure if Augustine's claim
'all your years stand simultaneously'
is true or not, I am not even sure I understand what that statement means in real time.
That comes with its own problem. In this 'outside time' place there must be some kind of meta-time, otherwise there'd be no time. And if no time, then no change of any kind, simply the statis of a old photograph.
The teaching may be verified fairly clearly, whether this is accepted or not. Our reality is a subset to the original one according to the teaching; i.e. it is a created one, perhaps even a virtual one in a sense. (this last thing is just ruminations of my own.) The teaching is that there is a beginning to time, and that beginning began when God began creating, in this case, created the first being, a copy of himself where we see the sun and moon being held up as examples, metaphors, of the original and the copy.
Example - useless or useful?
If you create a universe in your imagination. This universe contains only one thing, being it a sphere or a cube, take your pick. That is the extend of the contents of this universe.
Can it move, up down, right left, forwards backwards? No! It cannot. Can it rotate? No. It cannot. Does it experience time? Most likely not.
It lacks exterior reference points for any of the things just mentioned to occur.
Speaking with the only kind of logic I have, human, it seems that until God created another being to create a reference point, that time didn't exist in the way we understand it. He might have experienced internal time keeping if he has an internal mechanism and reference points.
Whatever the case is, the teaching is that time had a beginning back at that point.
I am sure that I am in over my head in this.
Possible scenarios
There is a scripture that could be interpreted as meaning that all creation is inside of God; of course, other interpretations might be possible.
Even the Big Bang theory postulates that for our universe, time began at its inflation. That is as far as my studies are concerned and have been postulated by scientists. Since many now espouse the idea of a multiverse, this could mean that time began for each universe, each pane, at different times when related to the whole multiverse.
Thus, the idea that time had a beginning is not unique.