Ringo officially became a Beatle on August 18, 1962. Here’s a great interview with Beatles biographer Bob Spitz about how it was only when Ringo replaced Pete Best that the group coalesced into the Fab Four that would take the world by storm (from FaceCulture).
Spitz: “By the time I finished working on the book eight and half years later, I realized the true hero of the Beatles’ story was Ringo Starr. He was a lovely guy, the other Beatles loved him unconditionally, he never had a bad word to say about anybody, he loved being a Beatle, he was a fantastic drummer, and he only ever wanted what was best for the group. And so Ringo, I think, is the true hero of this book and for me he came out at the end as really the character I could identify with the most. And, funnily enough, I found out that when the Beatles first came to the United States, they were selling those buttons, ‘I love John,’ ‘I love Paul.’ The ‘I love Ringo’ buttons out sold the others five to one. So maybe Ringo has all the magic of the story, maybe he isn’t just the luckiest man alive.”