22 February 1964: broadcast of "The Roof of the World", first episode of the story we now call Marco Polo. Trapped in the snow, the time travellers are rescued by Marco Polo, who however impounds the Tardis.
22 February 1969: broadcast of fifth episode of The Seeds of Death. the Doctor and friends get back to Earth and discover that the Ice Warrior' pods are disabled by water.
22 February 1975: broadcast of first episode of The Sontaran Experiment The Doctor, Sarah and Harry discover that a bunch of
22 February 1982: broadcast of third episode of The Visitation. The Terileptils plan to destroy humanity, and do destroy the sonic screwdriver.
22 February 1983: broadcast of third episode of Terminus. The Doctor realises tha the ship's fuel dump actually caused the Big Bang.
22 February 2002: webcast of second part of "Planet of Blood", the third episode of Death Comes to Time. Horrible slaughter discovered by the Doctor and Antimony in London; meanwhile Ace is undergoing mysterious training and there's a time lord played by Stephen Fry. (I found it all a bit confusing.)