i) births and deaths

16 July 1924: birth of Robert Banks Stewart, author of both Terror of the Zygons (Fourth Doctor, 1975) and The Seeds of Doom (Fourth Doctor, 1976).

16 July 1974: birth of Mark Tonderai, director of The Ghost Monument and Rosa (both Thirteenth Doctor, 2018). He was the first black director of a Doctor Who story (though not the first person of colour – that would be Waris Hussein back at the very beginning).

16 July 2017: death of Trevor Baxter, who was only in one TV story, The Talons of Weng Chiang (Fourth Doctor, 1977) but reprised the role of Professor George Litefoot in literally dozens of Big Finish audios.

ii) broadcast anniversary

16 July 2018: announcement of Jodie Whittaker as the Thirteenth Doctor. Still sends shivers down my spine.

ii) and iii) broadcast anniversary and date specified in-universe

16 July 1966 was that day that the last episode of The War Machines, which was also the last episode of the original third season, was broadcast. The Doctor invents a way of neutralising the War Machines, defeats WOTAN, learns that Dodo is staying in England, and takes off with new companions Ben and Polly unintentionally on board.

16 July is also specified in the script of The War Machines as "C-Day", the day when all the computers in the world are to be linked (and then WOTAN will rule supreme). The problem is, Sir Charles Summers specifies very clearly in Episode 1 that C-Day will be on Monday 16 July; and 16 July 1966 was, obviously since Doctor Who was on telly that evening, a Saturday – the next Monday 16 July was in 1973 (and the previous one, in 1962, is impossible because the Post Office Tower had not yet been built). For reasons we shall explore in a couple of days, this creates other problems. I prefer to think that Sir Charles misspoke and meant Saturday, or the 18th, and the journalists at the press conference were too polite to correct him. This would make them rather unusual journalists, but Doctor Who is a show about unusual people.