30 December 1970: birth of Saul Metzstein, director of several Eleventh Doctor stories.
30 December 2011: wedding of David Tennant and Georgia Moffett.
30 December 1996: birth of Vivian Oparah who played Tanya Adeola in Class.
30 December 1967: broadcast of second episode of The Enemy of the World. Giles Kent asks the Doctor to help him against Salamander. Jamie and Victoria manage to infiltrate Salamander's headquarters.
30 December 1972: broadcast of first episode of The Three Doctors, starting Season 10 and bringing back Patrick Troughton and William Hartnell. The Time Lords are losing energy; UNIT is besieged by strange special effects and the First and Second Doctors return.
30 December 1978: broadcast of second episode of The Power of Kroll. Kroll starts grabbing people with his tentacles.
iii) date specified in-universe
30 December 1999: the Seventh Doctor arrives in Los Angeles and is immediately shot in gang war crossfire; he later dies on the operating table. (As seen in The Movie, 1996)