Date Event Related Anime
February 1 Holy Grail War Fate/Stay Night
February 28 Pluto’s Kiss .hack
Night between April 30 and May 1 Walpurgis Night Madoka Magica
Third Sunday of June Watanagashi Festival Higurashi
August 13 Time Leap machine completed Steins;Gate
September 13 Second Impact Neon Genesis Evangelion
September 28 Ending spoiler Code Geass
October 31 Halloween Umineko
November 23 Light finds the Death Note Death Note
December 18 Haruhi’s disappearance The Disappearance of Haruhi Suzumiya

Did I miss anything? Let me know!