Creation -The Genesis Account
How long has God existed?
God is eternal, and has always existed. Time is the 4th dimension, which He created on the First Day of Creation (see under The Genesis Account Of Creation - The First Day). God lives in eternity, which is outside space time completely.
This is stated in the following 3 verses, amongst many others:
Isaiah 57:15: "Thus says the High and Lofty One Who inhabits eternity, whose name is Holy: "I dwell in the high and holy place."
Revelation 1:8: "I am the Alpha and the Omega, the Beginning and the End," says the Lord, "who is and who was and who is to come, the Almighty."
Colossians 1:15-17, "Christ is the exact likeness of the unseen God. He existed before God made anything at all, and, in fact, Christ himself is the Creator who made everything in Heaven and Earth, the things we can see and the things we can't; the spirit world with its kings and kingdoms, its rulers and authorities; all were made by Christ for his own use and glory. He was before all else began and it is his power that holds everything together," TLB.