7 May 1908: birth of Valentine Dyall, who played the Black Guardian in 1979 and 1983 and Slarn in Slipback (1985).
7 May 1964: birth of Craig Hinton, author of several Who novels and a Big Finish Who audio, and inventor of the work 'fanwank'.
ii) broadcast anniversaries
7 May 1966: broadcast of "Don't Shoot the Pianist", second episode of the story we now call The Gunfighters. The Doctor is mistaken for Doc Holliday, with potentially fatal consequences for Steven.
7 May 2005: broadcast of The Long Game. The Doctor, Rose and Adam visit the far-future broadcasting hub on Satellite Five.
7 May 2011: broadcast of The Curse of the Black Spot.
iii) dates specified in canon
7 May 1915: sinking of the Lusitania, as depicted in second episode of The Sirens of Time, the very first Big Finish audio in 1999.
7 May 2157: the Daleks destroy Pluto's satellite Charon, as described in Craig Hinton's 1997 novel GodEngine.