28 February

28 February was a date.

In 1939, Earth was invaded by the Dord, a species of brain parasite that transported themselves through language. Fortunately, their invasion was limited to a single dictionary. (PROSE: Time Traveller's Diary)

In 1941, production on the Nazi aircraft Munin completed after half a decade's worth of work. (PROSE: Just War)

In 1981, the Fourth Doctor and Adric landed the TARDIS by the side of a motorway to measure a police box, as part of their plan to repair its chameleon circuit. On her way to work at London's Heathrow Airport, air hostess Tegan Jovanka stumbled aboard the TARDIS, mistaking it for a genuine police box, whilst seeking assistance for a flat tire. The TARDIS took off with her in it. The car's owner, Tegan's aunt Vanessa, was murdered by the Tremas Master.

The Doctor and the Master later confronted one another on the Pharos Project, where the Doctor slipped and fell, resulting in him regenerating into his fifth incarnation. (TV: Logopolis; PROSE: Divided Loyalties)

On the same day, the TARDIS materialised on the Urbankans' spaceship, where the Fifth Doctor, Tegan, Nyssa and Adric found Urbankans and human androids. The Doctor saved the Earth from the leader of the Urbankans, Monarch, who had planned to poison humanity in order to steal equipment needed to travel in time. Having decided they would no longer have any place on Earth, the androids decided to pilot the ship to a new world and continue their lives there. (TV: Four to Doomsday)

Behind the scenes
This was one of very few instances in which a Doctor Who television story, namely part one of Logopolis, took place on the same day as its broadcast: 28 February 1981. Other such examples are 1 January 2019, 16 July 1966 and 26 June 2010.