The Hundred Light-Year Diary

"The Hundred Light-Year Diary" is a science-fiction short story by Australian writer Greg Egan, first published in Interzone 55 in January 1992. It was later published in the short story collection Axiomatic. It was a finalist for the 2007 Premio Ignotus for Best Foreign Story.

Plot
The discovery of Chen's galaxy moving backwards through time (due to time reversing with the upcoming contraction of the universe) allows the construction of a messaging system to send information into the own past (using mirrors and sending photons towards Chen's galaxy). Every human is granted a hundred words a day to get send back a hundred years after their death to have a diary of their entire life from birth. James, after already having met his future wife Alison just as described in his diary, starts an affair with a woman, who doesn't keep a diary at all, none of which was mentioned in his own. James instead begins to write lies about his relationship with Alison, hence the upcoming bitterness within is not being reflected in his cheerful messages at all. When war breaks out, he begins to wonder about large scale lies from the future and whether he can change anything at all.

Reception
Karen Burnham, writing in the New York Review of Science Fiction, considers the short story to be among the "rather depressing' ones of Greg Egan because if anything can constrain our free will, it is the cold hand of physics in a closed universe".