i) births and deaths

6 March 1972: birth of Julian Simpson, director of The Rebel Flesh and The Almost People (Eleventh Doctor, 2011).

ii) broadcast anniversaries

6 March 1965: broadcast of "Crater of Needles", fourth episode of the story we now call The Web Planet. Ian and Vrestin meet the Optera; Barbara tries to link with the invading Menoptera but they are massacred by the Zarbi.

6 March 1971: broadcast of sixth episode of The Mind of Evil. The Thunderbolt missile and the Keller machine are both destroyed, but the Master escapes.

6 March 1976: broadcast of sixth episode of The Seeds of Doom, ending Season 13. The Krynoid grows to enormous size but is destroyed by the RAF.

iii) date specified in-universe

6 March 2006: setting of Aliens of London (Ninth Doctor, 2005).