In 2009 a PR company shifted the date of creation of Tetris by a year.
Before E3 2009, Tetris was on written record as being created in 1985.
For a party funded by Blue Planet Software (Bullet Proof Software) at E3 2009, the date was conveniently changed to 1984, curiously a very specific 6th June 1984, so they could celebrate the 25th Anniversary of Tetris a year early on 6th June 2009.
More info: June 6, 1984 | Tetrisconcept
And in those ~15 years since, the damage and confusion is still being seen. Just this week a book was relased, Video Game of the Year: A Year-by-Year Guide to the Best, Boldest, and Most Bizarre Games from Every Year Since 1977, featuring one game from each year since Pong was released. Tetris was featured for 1984. Oops.