We know that God elected individuals to Salvation because they as individuals believe in time, yet they were ordained to eternal life before time Acts 13:48
48 And when the Gentiles heard this, they were glad, and glorified the word of the Lord: and as many as were ordained to eternal life believed.
Eternal Life was promised before the world began Titus 1:2
2 In hope of eternal life, which God, that cannot lie, promised before the world began;
Now who was it promised to but to them He ordained to eternal life
Now the actual persons ordained to eternal life were not in actual existence, yet their Covenant Head and Sponser Christ Jesus was, and it was to Him as their Head was the promise made, hence John writes 1 Jn 2:25
25 And this is the promise that he hath promised us, even eternal life.