Once Upon A Time (though I am using the word ‘time’ anachronistically, as time did not yet exist) there was Eternity. Eternity has no beginning, and no end. It is not, properly speaking, part of creation: it has always been, as a consequence of God’s being; and it has no being independent of God.
And then there was Time. Time had a beginning, in creation, as a consequence of God creating the day and the night, the seasons and days and years.
At first, time and eternity were woven together. There was no death, no ending: no history. But then something happened: the man and the woman rebelled against God; and, as a consequence, for the good of the man and the woman and all creation (for God loved his creation), God drove eternity and time apart (for to live in eternity in rebellion to God would have unimaginably bad consequences). And with time left alone without eternity, history began.
Just occasionally, God would allow someone to cross over from time into eternity (Enoch; Elijah), cheating death, defying history. Just occasionally, God would cross over from eternity into time (appearing to Abraham; to Gideon). But then something happened: the darling of heaven submitted to the Father’s will; and, as a consequence, for the good of men and women and all creation (for God loves his creation), eternity and time were reunited (for to live in eternity in submission to God would have unimaginably good consequences). Death and history made their stand: and, indeed, succeeded in killing the Son. God died  (and with him, eternity; for eternity has no being independent of God). But death and history were not strong enough to hold God, and three days later he returned  (and with him, eternity; for eternity is a consequence of God’s being). And with time being woven together again with eternity, history came to an end.
With eternity – before and alongside and after time - being reconciled to time by the One who is reconciling all things to himself, the One who was and is and is to come (not merely the One who always is) invades and transforms the present.
To observe the season of Advent is to live simultaneously in a reality where Jesus has not yet come (anticipating the Feast of Christmas) and where Jesus has already come again (in the light of what is yet to come; for faith is the substance of what we hope for, Hebrews 11:1). And that reality transforms the present, where we remember his coming and await his coming again…
This is the stuff of True Myth (as CS Lewis and JRR Tolkien both knew).
 We can say God died, because the Son is consubstantial with the Father: they are of one substance. To say that God was dead and returned is not to deny that the Father raised the Son to life. All language that speaks of God is inadequate, even when it is true.