19 March 1966: broadcast of "The Return", third episode of the story we now call The Ark. The Tardis returns to the Ark centuries after its original visit, to find that the Monoids are now in charge. The Doctor and Dodo are sent to investigate Refusis.
19 March 1977: broadcast of fourth episode of The Talons of Weng-Chiang. The Doctor escapes from Li H'sen Chang on stage; Weng-Chiang's men capture the Time Cabinet from Litefoot's house.
19 March 2005: broadcast of the Doctor Who night on BBC.
19 March 2008: broadcast of Adrift (Torchwood), the one with the island full of people rescued from Torchwood's vault by Jack.
ii) date specified in canon
19 March ?2009: setting of From Out of the Rain (Torchwood, 2008).