1st September 1974: birth of Burn Gorman, who played randy (and later undead) medic Owen Harper in the first two series of Torchwood (2007-2009).
ii) broadcast anniversary
1st September 1979: broadcast of episode 1 of Destiny of the Daleks, opening episode of Season 17. Romana regenerates; the Tardis lands on
1 September 2012: one of the most successfully unspoilered twists ever as Jenna-Louise Coleman prequels her future companionship in Asylum of the Daleks, the first story of Ne Who series 7 with the Eleventh Doctor.
iii) dates specified in spinoff literature
1st September 1991: happens over and over again in the Suffolk town of Thorington. Incidentally, what happened to the sea? (as told in the 2008 Eighth Doctor audio play, Brave New Town)
1st September 2982: funeral of Eighth Doctor Adventure companion Roz Forrester (in Ben Aaronovitch and Kate Orman's 1997 novel, So Vile a Sin).