John Titor supposedly time travels back to the winter of 1975 to retrieve an IBM 5100 computer which he claimed was needed to "debug" various legacy computer programs in 2036.
According to Lt. Commander Data in the pilot episode of Star Trek: The Next Generation, this year the United Nations resolved that "No person shall be made to answer for the crimes of their race or forebears." The entity Q scoffs at this, saying this was a court of 2079, when the U.N. no longer existed. Complicating this argument is that the date of 2079 in Trek lore is 16 years after the events of Star Trek: First Contact, when extraterrestrial life has already been discovered and is assisting humanity to recover from the Third World War.