Eternity is prior to time. This is not to say that eternity is before time; “before” is a temporal relation. Eternity happens prior to time in the order of logic, rather than in the order of time. So, eternity is happening right now. This is true at all nows.
Eternity, then, subvenes all times. But this means that, from the perspective of any particular instant of time, eternity is prior to it in time. It is the concrete contemporaneity of eternity with all the prior moments that contribute causally to a given instant of time that makes it proper to say straightforwardly that eternity is “ante omnia saecula,” as the Creed has it.
That God is eternal does not mean he is not also in time. There is no contradiction between the two modes of being, temporal and eternal; if there were, then there would no way to have temporality in the first place, for time is happening in eternity, and is fully limited by and conformed thereto
So, God responds to us in time, just as we respond to each other. His response is happening in time and in eternity – they are not different, because time is an operation of eternity. So Jesus is in time as we are, but he is also consciously eternal. The Incarnation happened before all worlds, and is effectual for all worlds (so that by their very existence they all presuppose it) because all worlds happened before all worlds (in this consists the divine foreknowledge, and from this proceeds the divine providence); the happening of worlds is entirely a procedure of eternity.
I discuss this topic in much greater detail here.