6 May 1945: birth of Nicholas Mallett, who directed The Mysterious Planet (1986), Paradise Towers (1987) and The Curse of Fenric (1989).
6 May 1976: death of Alethea Charlton, who played Hur in An Unearthly Child (1963) and Edith in The time Meddler (1964).
ii) broadcast anniversaries
6 May 1967: broadcast of fifth epside of The Faceless Ones. The Chameleons explain that they lost their identities. In an explosion.
6 May 1972: broadcast of fifth episode of The Mutants. The Marshal forces the Doctor to work for him by holding Jo hostage.
6 May 2006: broadcast of The Girl in the Fireplace. The Doctor, Rose and Mickey land on a far future spaceship and the Doctor become involved with Madame de Pompadour.
iii) date specified in canon
6 May 1997: setting of Lance Parkin's Virgin New Adventure The Dying Days, featuring the Eighth Doctor and Bernice Summerfield.