God is indeed unchanged and unaffected by time (in fact, time is in subjection to His purposes), but this does not mean that He exists in some far off realm or “other dimension” called eternity, as some would foolishly render
Isaiah 57:15 to mean. Rather, “inhabiteth eternity” speaks on this wise: concerning one of His divine attributes—that He lives
(continues; exists; remains; abides; tarries; endures) forever and ever, and that God was before the world (ages) began; before He created all things. As Paul wrote to Timothy, God “only hath immortality”.
20 Now, eternity refers not only to that which was before the world began, but also that which shall be after this present world ends. God, not a “spiritual plane” in some hypothetical “other universe”, is the subject which eternally lives (and who has promised immortality freely to all those who love Him).