4 March 2016: death of Terence Woodfield, who appeared in two different First Doctor stories in 1966: as Celation in the story we now call The Daleks' Master Plan, and as Maharis in the story we now call The Ark
ii) broadcast anniversaries
4 March 1967: broadcast of fourth episode of The Moonbase. The Doctor defeats the Cybermen by using the gravitron to make them float away into space.
4 March 1972: broadcast of second episode of The Sea Devils. The Doctor and Jo escape the the nearby sea base and discover that the Master is stealing equipment.
4 March 1978: broadcast of fifth episode of The Invasion of Time. The Doctor and friends escape, and the Doctor persuades Borusa to let him have the Great Key.
iii) date specified in-universe:
4 March 2005: setting of the opening part of Rose, the first Ninth Doctor story.