On Sunday, 31 March 1963, Susan Foreman witnessed her grandfather talking casually to the Cold outside the TARDIS. He seemed unfazed about them wanting to wipe out the humans, still stuck to the Time Lords' non-interference policy despite having escaped Gallifrey to get away from all that. This worried Susan. (PROSE: Time and Relative)
UNIT released an embargoed press briefing on 31 March 2005, filed by Staff Sergeant A. Frederick, about Major A Highway's plan to reorganise UNIT's pan-territorial activities in America into a single site operation, (PROSE: UNIT's New York Operation Expansion) the New York UNIT HQ. (TV: The Stolen Earth, COMIC: The Fountains of Forever)
In 2040, Imogen Quaye began to get into literature, Shakespeare in particular. As a result of this, she felt "[better] than [she'd] felt in years," "sort of bigger inside." (PROSE: Artificial Intelligence)
Behind the scenes
The "present day" opening of the film Daleks' Invasion Earth 2150 A.D., which sees Tom Campbell join Dr. Who in TARDIS, takes place on 31 March of an unidentified year.