Roald Dahl was born on September 13, 1916.
There are very few children's writers whose accomplishments are so great, that there's no need to list them. James and the Giant Peach has always been one of my favorite books for any age group. Even now that I'm old enough that even my kids' childhoods are behind them, James is a great read. If he had written nothing else, Dahl's birth would still be worth celebrating. Of course he wrote more. A lot more.
Charlie and the Chocolate Factory, Matilda, The Witches--it's a long list: 17 children's stories, three volumes of children's poetry, two adult novels, 19 short story collections, several non-fiction books, a play, six movies (including the screenplays for "Chitty Chitty Bang Bang" and the 1971 version of "Willie Wonka and the Chocolate Factory,"and a bunch of TV episodes including several episodes of Alfred Hitchcock Presents, Tales of the Unexpected, and his own series, Way Out.
But Dahl was more than a writer. A fighter pilot for the RAF in WWII, Dahl's victories earned him the title of Flying Ace. He also became known for his controversial stance against Israel (although, he claimed not against Jews).
Dahl was truly a transformational author. His influence on other writers is obvious. It's possible that no author has influenced current writers, especially middle grade authors, as much as Roald Dahl.