7 August 1924: birth of Kenneth Kendall, who appeared as a newsreader in The War Machines (1966), the first celebrity to portray himself on Doctor Who (unless you count the Beatles). He's also in 2001: A Space Odyssey in a similar role.
7 August 1952: birth of Alexei Sayle, who plays the DJ in Revelation of the Daleks (1986). 'Allo John, got a new motor? Is there life on Mars? Is there life in Peckham?
7 August 1966: birth of Shobna Gulati, who plays Yaz's mother Najia Khan in several Thirteenth Doctor stories (2018 and 2020).
7 August 1999: death of Ric Felgate, who appeared in three stories all directed by his brother-in-law Michael Ferguson. He was Roy Stone, an American journalist in The War Machines (First Doctor, 1966), Brent, killed by the Ice Warriors in The Seeds of Death (1969) and astronaut Charles Van Lyden, the first person seen on screen in The Ambassadors of Death (Third Doctor, 1970).
7 August 2014: death of Michael Kerrigan, who directed Battlefield (Seventh Doctor, 1989) and also the 2008 Sarah Jane Adventures stories The Day of the Clown and Secrets of the Stars.
ii) broadcast anniversaries
iii) dates specified in-canon
7 August 1941: setting of the WW2 bit of the Torchwood comic story Overture, published in the 25th and last issue of Torchwood Magazine, by Gary Russell with art by John Ridgway and letters by John Workman.