The Bible describes God's relationship to time in several places. Psalm 90:4 says, "For a thousand years in your sight are but as yesterday when it is past, or as a watch in the night." Second Peter 3:8 says, "…with the Lord one day is as a thousand years, and a thousand years as one day." Isaiah 57:15 says that God "inhabits eternity."
What is the relationship between God and time?
When we say things like "God is timeless" or "God has no beginning or end," we are trying to explain God in terms of a dimension by which He is not constrained. God created time.
In our universe time is basically linear. We go forward at a fairly steady rate, give or take allowances for velocity and gravity. We cannot go back in time, and we cannot experience more than one instant at a time.
God does not have this limitation. He does not live within the semi-linear timeline of our universe. He experiences every moment of time all at once. It is similar to the creator of an animated film. While the film is running, the characters experience life one cel (the sheet on which animations are drawn) at a time as it flickers past the light. But the animator lives in a dimension where all the cels exist at once, and he can view them all at will.
Understanding this gives us a better understanding of God's power in our lives. He was able to create the world in six days because days do not confine Him or His work (Genesis 1). He was able to choose who to save before the ages began (2 Timothy 1:9) because He created the ages. And He is able to select good works for us to do ahead of time (Ephesians 2:10) because He can see everything that will ever happen in human history and exactly how we can be the most effective to use that history to bring people to Him. When He says He has a "plan" for us (Jeremiah 29:11) that plan is based on His perfect knowledge of all of history, present, and future. When we don't trust His plan, it is the ultimate foolishness – like ignoring the advice of a perfect GPS because we think we know a better route.
God's timelessness is part of His perfection. He has no need of growth or development or any of the other benefits linear time gives us. He also has no temporal beginning or end. He has neither our need for time nor our time-related limitations, which is just another example of why we can trust Him with our short temporal lives.
Who created God?
What was God doing before creation?
Does God change His mind?
Does God make mistakes?
Is God immutable? What is the significance of the immutability of God?
Truth about God