16 May 1963: date of a note with the title '"Dr. Who" General Notes on Background and Approach for an Exciting Adventure - Science Fiction Drama Series for Childrens Saturday Viewing', signed by Donald Wilson, C.E. Webber and Sydney Newman. Click to embiggen.
16 May 1964: broadcast of "The Keys of Marinus", sixth episode of the story we now call The Keys of Marinus. Susan, Barbara and the Doctor expose Eyesen and Kala and liberate Ian; the Voords have taken over the Conscience, but Ian gives them a false key and it explodes.
16 May 1970: broadcast of second episode of Inferno. More slime bubbles up, infecting Stahlman; and the Doctor vanishes, with Bessie and the Tardis console.
16 May 2003: webcast of second episode of Shada. The Doctor, Romana, K9 and Chris find Skagra's invisible spaceship.
16 May 2013: release of Strax Field Report - The Name of the Doctor.