God said: …”Time is a convenient way to talk about things. Space is a convenient way as well. In fact, in the world, space is seen as solid. One who is not solid may be seen as spacey. You are neither timey nor spacey, for neither exists.” HL 4259
This instant well known now as the Big Bang is equivalent to a millionth of a billionth of a billionth of a second, that is 10-24 seconds.
We could even say that it happened all at once.