12 July 1928: birth of Frank Windsor, who played Ranulf Fitzwilliam in The King's Demons (Fifth Doctor, 1983) and Inspector Mackenzie, who ends up in the soup in Ghost Light (Seventh Doctor, 1989). He was better known for playing policeman James Watt in various BBC dramas from 1962 to 1976 - Z-Cars, Softly Softly and Softly Softly Taskforce. NB that https://tardis.wikia.com gives his year of borth as 1927, but other sources give 1928. Happy ninety-somethingth birthday, Frank!
12 July 1933: birth of Brian Cant, who I knew as one of the great BBC children's presenters of the 1970s but before then had appeared in The Daleks' Master Plan (First Doctor, 1965) as Kert Gantry and The Dominators (Second Doctor, 1968) as Tensa. Both characters are doomed. His son Richard Cant turns up in Blink (Tenth Doctor, 2007) as Kathy Nightingale's grandsom Malcolm.
12 July 1980: birth of Tom Price (PC Andy in Torchwood).
12 July 1995: death of Gordon Flemyng, director of Dr. Who and the Daleks (1965) and Daleks' Invasion Earth: 2150 A.D. (1966)
ii) broadcast anniversaries
None. (The first day I'll write up that briefly, but not the last - August is a particularly thin month.)
However, it was on this day in 1963 that William Hartnell first met with Verity Lambert and Waris Hussein to discuss his possible role in her new show.
iii) date almost specified in-universe
12 July 1966: It is roughly about this date that WOTAN starts getting active in The War Machines (1966) - four days before "C-Day", and by extension, Ben Jackson meets Polly at the Inferno night club the same evening. But more of that anon...
iv) date specified implicitly in-universe
The earliest of the date stamps on the base seen in The Doctor's Daughter (Tenth Doctor, 2008), and correctly interpreted by Donna, is for 12 July 6012. They go up to the 24th.