God dwells in eternity but time dwells in God. He has already lived all our tomorrows as He has lived all our yesterdays. An illustration offered by C. S. Lewis may help us here. He suggests that we think of a sheet of paper infinitely extended. That would be eternity. Then on that paper draw a short line to represent time. As the line begins and ends on that infinite expanse, so time began in God and will end in Him.
