The 35th of May, or Conrad's Ride to the South Seas (Der 35. Mai, 1931 in German, its original language) is a novel by Erich Kästner, first published in 1931.
The novel is about Conrad, a young boy, who spends each Thursday with his uncle, Mr. Ringelhuth. One Thursday - it happens to be the 35th of May - they meet Negro Caballo, who is well-versed in German literature, and at the same time, is the best roller skater in the world. Negro Caballo is a black horse that can speak. Together they enter Uncle Ringelhuth's huge wardrobe, which stands in the hallway, and end up on a thin strip of metal, which is the Equator. The starting pont of the Equator is the wardrobe itself. Conrad and his uncle mount Negro Caballo, and together they travel - or rather roller-skate - along the Equator to many parts of the world, gathering interesting and sometimes hair-raising experiences.