i) births and deaths

23 March 1909: birth of Charles Morgan, who played Songsten in The Abominable Snowmen (Second Doctor, 1967) and the Gold Usher in The Invasion of Time (Fourth Doctor, 1978).
23 March 1928: birth of Louis Marks, who wrote Planet of Giants (1964), Day of the Daleks (1972), Planet of Evil (1975) and The Masque of Mandragora (1976).

23 March 2018: death of Rupert Laight, writer of two Sarah Jane Adventures TV stories and of various bits of spinoff fiction, most of them rather good. I had missed the memo about this - he cannot have been old.

23 March 2020: (this one I do remember, sadly) death of David Collings, who played Vorus in Revenge of the Cybermen (Fourth Doctor, 1975), Poul in The Robots of Death (Fourth Doctor, 1978), and Mawdryn in Mawdryn Undead (Fifth Doctor, 1983). He also played an alternate Doctor in the 2003 Big Finish audio Full Fathom Five, by Gary Russell.
ii) births and deaths

23 March 1968: broadcast of second episode of Fury from the Deep. Maggie Harris is overpowered by Oak and Quill, and the mysterious noises intensify.
23 March 1974: broadcast of first episode of The Monster of Peladon. The Doctor and Sarah land on Peladon to find Queen Thalira having problems with the miners.
23 March 1982: broadcast of second episode of Time-Flight. The mysterious Kalid has been kidnapping Concordes. Guess who he really is???
23 March 1984: broadcast of second episode of The Twin Dilemma. The Doctor meets an old friend, but discovers that he is responsible for kidnapping the twins.
23 March 1985: broadcast of first episode of Revelation of the Daleks. At Tranquil Repose, there is a disc jockey who looks just like Alexei Sayle and people being turned into Daleks.