God is God. God has always existed and always will. Jesus is God’s son and has always existed with God.
In the scope of eternity, what is a little change?
Let us think on that.
You can endure change by pondering His permanence. ~Max Lucado
The author of Hebrews has some insight to offer.
And, “You, Lord, laid the foundation of the earth in the beginning,
and the heavens are the work of your hands;
they will perish, but you remain;
they will all wear out like a garment,
like a robe you will roll them up,
like a garment they will be changed.
But you are the same,
and your years will have no end.
English Standard Version. (2016). (Hebrews 1:10–12). Wheaton, IL: Crossway Bibles.
This long quotation comes from Psalm 102:25–27. The angels did not found the earth, for they too are a part of creation. Jesus the Messiah is the Creator, and one day He will do away with the old creation and bring in a new creation. Everything around us changes, but He will never change.
Jesus, the Son of God, is “the same yesterday, and today, and forever” (Heb. 13:8). Creation is like an old garment which will one day be discarded in favor of a new one.
God is our constant. We can count on God because God has always existed and always will.
Every good gift and every perfect gift is from above, coming down from the Father of lights, with whom there is no variation or shadow due to change.
James 1:17 (ESV)
When we think about the “big picture”, only God has that view. When God decides on a course of action, that is it. God will not change His mind.
but this one was made a priest with an oath by the one who said to him: “The Master [Lord] has sworn and will not change his mind, ‘You are a priest forever.’
Hebrews 7:21 (ESV)
We know we can count on the word of God. Everything else comes and goes. Not the word of God. Like God who utters it, it endures with God.
since you have been born again, not of perishable seed but of imperishable, through the living and abiding word of God; for “All flesh is like grass and all its glory like the flower of grass. The grass withers, and the flower falls, but the word of the Lord remains forever.” And this word is the good news that was preached to you.
1 Peter 1:23–25 (ESV)
God transcends all concepts of time
We live in a time oriented world. God does not. God can be constant because God existed before time. God has always had a plan. That plan existed before creation of the universe and man. We can count on God.
- Revelation 1:8 (ESV) — 8 “I am the Alpha and the Omega,” says the Lord God, “who is and who was and who is to come, the Almighty.”
- Psalm 90:4 (ESV) — 4 For a thousand years in your sight are but as yesterday when it is past, or as a watch in the night.
- Isaiah 41:4 (ESV) — 4 Who has performed and done this, calling the generations from the beginning? I, the Lord, the first, and with the last; I am he.
- 1 Corinthians 2:7 (ESV) — 7 But we impart a secret and hidden wisdom of God, which God decreed before the ages for our glory.
- Hebrews 13:8 (ESV) — 8 Jesus the Messiah [Christ] is the same yesterday and today and forever.
- 2 Peter 3:8 (ESV) — 8 But do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day.
- Revelation 11:17 (ESV) — 17 saying, “We give thanks to you, Lord God Almighty, who is and who was, for you have taken your great power and begun to reign.
- Revelation 22:13 (ESV) — 13 I am the Alpha and the Omega, the first and the last, the beginning and the end.”
Digging Deeper – Is God eternal in nature?
If you want to dig deeper, here are some additional resources. The word eternal means “everlasting, having no beginning and no end.” Psalm 90:2 tells us about God’s eternality: “Before the mountains were born or you brought forth the earth and the world, from everlasting to everlasting you are God.”
- Since humans measure everything in time, it is very hard for us to conceive of something that had no beginning, but has always been, and will continue forever.
- However, the Bible does not try to prove God’s existence or His eternality, but simply begins with the statement
- “In the beginning God…” (Genesis 1:1), indicating that at the beginning of recorded time, God was already in existence.
- From duration stretching backward without limit to duration stretching forward without limit, from eternal ages to eternal ages, God was and is forever.
Now to him who is able to keep you from stumbling and to present you blameless before the presence of his glory with great joy, to the only God, our Savior, through Jesus the Messiah [Christ] our Master [Lord], be glory, majesty, dominion, and authority, before all time and now and forever. Amen. 
Wayne Grudem Systematic Theology
God’s eternity may be defined as follows: God has no beginning, end, or succession of moments in his own being, and he sees all time equally vividly, yet God sees events in time, and he acts in time.
Sometimes this doctrine is called the doctrine of God’s infinity with respect to time. To be infinite is to be unlimited, and this doctrine teaches that time does not limit God.
This doctrine is also related to God’s unchangeableness. If it is true that God does not change, then we must say that time does not change God; it has no effect on his being, perfections, purposes, or promises. But that means that time has no effect on God’s knowledge, for instance. God never learns new things or forgets things, for that would mean a change in his perfect knowledge. This implies also that the passing of time does not add to or detract from God’s knowledge. He knows all things past, present, and future and knows them all equally vividly.
The concept of eternity, then, does not stand in opposition and contrast to time as timelessness. Eternity is the unlimited and incalculable space of time bounded at its beginning by the introduction of the kingdom of God in Christ and stretching out into the unlimited future. Both time (“the present evil age,” Gal 1:4) and eternity are governed by God as the Lord of all time, the one who gives content and meaning to both. For the believer the midpoint of time (even though the second coming of Christ and the consummation of the present eon have not yet occurred) is found in the first Easter. It is not the consummation that brings eternity; eternity is the accomplishment of God’s sovereign and eternal purpose in Christ for the whole universe.
Holman Treasury of Key Words
The concept of eternity, then, does not stand in opposition and in contrast to time as timelessness. Eternity is the unlimited and incalculable space of time bounded at its beginning by the introduction of the kingdom of God in Christ and stretching out into the unlimited future. Both time, or “the present evil age” (Gal. 1:4), and eternity are governed by God as the Lord of all time—the one who gives content and meaning to both. As believers in Christ, we have eternal life and will indeed live forever with Him.
International Standard Bible Dictionary
In the OT, God’s eternity is only negatively expressed, as implying merely indefinitely extended time (Gen 21:33; Dt 33:27), though Isa 40:28 takes more absolute form. Better is the view of eternity, objectively considered, as a mode of being of God in relation to Himself. For He was eternal, while as yet the world and time were not. But even in the NT, the negative form of expression prevails. Time, with its succession of events, helps to fill out such idea as we can form of the eternal, conceived as an endless progress. But, as finite beings, we can form no positive idea of eternity. Time is less contradictory of eternity, than helpful in revealing what we know of it. Plato, in his Timaeus, says that time is the “moving image of eternity,” and we may allow that it is its type or revelation. Not as the annulment of time, though it might be held to be in itself exclusive of time, is eternity to be taken, but rather as the ground of its reality.
 Grudem, W. (2020). Systematic Theology: An Introduction to Biblical Doctrine (Second Edition, p. 199). Grand Rapids, MI: Zondervan Academic.
 Carpenter, E. E., & Comfort, P. W. (2000). In Holman treasury of key Bible words: 200 Greek and 200 Hebrew words defined and explained (p. 275). Nashville, TN: Broadman & Holman Publishers.
 Lindsay, J. (1915). Eternity. In J. Orr, J. L. Nuelsen, E. Y. Mullins, & M. O. Evans (Eds.), The International Standard Bible Encyclopaedia (Vol. 1–5, p. 1011). Chicago: The Howard-Severance Company.