Cern, creators of the World Wide Web, announced that it could be used for free by anyone.
Birth of Lionel Hampton, American musician (Note: this date is given by most sources, but Encyclopaedia Britannica lists it as 12th Apr 1913).
The celebrated case of Ashford v Thornton ended when Ashford withdrew having declined to submit to trial by battle, a statute that had never been repealed.
Captain Cook discovers the East coast of Australia, his log recorded 19th April but correcting for the international date line the calender date is the 20th.
Jacques Cartier set sail on the voyage that would lead to the official discovery of Canada and Labrador.