Halloween
From Tardis Wiki, the free Doctor Who reference
Halloween was a human holiday traditionally celebrated on 31 October.
On Halloween 1938 Orson Welles broadcast a radio play adaptation of H. G. Wells' novel The War of the Worlds, convincing certain members of the American population that Mars had really invaded. (BFA: Invaders from Mars)
On Halloween 2009, the Hervoken tried to take over the New England town of Blackwood Falls. (NSA: Forever Autumn)
On the same day, Torchwood Three had to deal with alien predators. (TWN: Pack Animals)