Correction: Ten years ago I listed this as being Alexander Armstrong's birthday, which it isn't. Can't find anyone else who satisfies my usual criteria.
ii) broadcast anniversaries
14 August 2011: release of the prequel for Let's Kill Hitler.
iii) date specified in-universe
14 August 1819: The Fifth Doctor, Nyssa and Tegan land in the outskirts of Manchester, in 2016 Big Finish audio The Peterloo Massacre.