C.S. Lewis described himself as converted to Christianity in 1931.
His religious development was gradual rather than a single simple moment. Lewis had returned to belief in God by 1929, and in 1931 he moved from theism to Christianity. Conversations with friends including J.R.R. Tolkien and Hugo Dyson helped shape his understanding of Christian belief during this period.
Lewis later wrote about his conversion in autobiographical works such as Surprised by Joy. Readers sometimes assign different dates because his journey included several stages: rejecting Christianity in youth, returning to belief in God, and then embracing Christianity. The year 1931 is the standard date associated with his conversion to Christianity.