i) births and deaths
19 July 1982: Death of John Harvey, who played Professor Brett in The War Machines (First Doctor, 1966) and Officia in The Macra Terror (Second Doctor, 1967)
ii) broadcast aniversaries etc
19 July 1999: release of the very first Big Finish audio, The Sirens of Time, featuring Peter Davison, Colin Baker and Sylvester McCoy. I have quite literally lost track of Big Finish's output - masses of material, including books as well as audio plays, reflecting all eras of the show and many spinoffs. More power to them.
iii) dates specified in-universe
19 July 1553: Rani finds herself in the court of Lady Jane Grey, and is appointed a Lady-In-Waiting, just as the army of Mary Tudor arrives to overthrow her, as seen in Lost in Time (Sarah Jane Adventures, 2010)
19 July 1843: date of the Cleansing, the point of departure for the alternate timeline in the Eighth Doctor novel Reckless Engineering.
19 July 2013: Tanya Adeola is informed by Coal Hill School that she can move forward three years due to her "truly extraordinary academic capability", as seen in flashback at the beginning of Nightvisiting, for my money the best single episode of Class (2016).