C.S. Lewis’s conversion to Christianity is generally dated to 1931.
Lewis had returned to belief in God several years earlier, but in 1931 he became a Christian. Conversations with J.R.R. Tolkien and Hugo Dyson were important in his movement toward Christian belief, particularly discussions about myth, history, and the meaning of Christ.
Lewis’s conversion was not an overnight change from atheism directly to a fully developed public ministry. His intellectual and religious outlook evolved through stages, and he later described parts of that journey in autobiographical works such as Surprised by Joy.
The year 1929 is associated with his belief in God, while 1931 is associated with his conversion to Christianity. The distinction matters because simplified biographies sometimes compress these separate milestones into one date.