C.S. Lewis identified 1931 as the year of his conversion to Christianity.
Lewis had returned to belief in God by 1929, but he later described a further conversion to Christianity in 1931. In his autobiographical writings, he recalled a conversation and a journey to Whipsnade Zoo with J.R.R. Tolkien and Hugo Dyson around this period. Their discussion helped him reconsider the relationship between myth, imagination, and Christian belief.
The dates can be confusing because Lewis’s return to theism and his conversion to Christianity were separate stages. He became a theist in 1929 and regarded 1931 as the decisive year of his Christian conversion.
That change influenced nearly all of his later work, including Mere Christianity, The Problem of Pain, and The Chronicles of Narnia. Lewis did not abandon literary imagination after converting; he used it as a way to explore moral and spiritual ideas.