29 April 1967: broadcast of fourth episode of The Faceless Ones. Jamie gets on a Chameleon plane, which is duly captured by the aliens.
29 April 1972: broadcast of fourth episode of The Mutants. The Marshal plans to bombard Solos with ionising rockets; Varan and his men prevent him but the Skybase is damaged.
29 April 2006: broadcast of School Reunion. The Tenth Doctor unexpectedly meets Sarah Jane Smith, thirty years on. (Sob!)
Perhaps people are getting fed up with Facebook?