In the book The Lathe of Heaven, by Ursula K. Le Guin, the main character, George Orr, can change the past through his dreams. But since your subconscious is in charge while you are dreaming, the changes he makes to are simple and direct. His therapist starts hypnotizing his and tries to use George's gift to solve the world's problems, but with mixed results.

George comments that, "Suppose you hypnotized me and told me to dream that there is a blue dog in the office. When I woke up, there would be a blue dog there, but it would be because something blue had splaches onto it, or, way back in prehistoric times, something happened which made dogs evolve to be the color blue. What I am saying is, when I wake up, only I will remember that before I went to sleep there were no blue dogs. To everyone else it would seem perfectly normal. You have to frame the instructions simply."

Example: his therapist tells him to solve overpopulation. George dreams that he is on a bus and there are hardly any people on it." He wakes up and finds that ten years ago a plague had hit the human race and kill three quarters of the population. And it is still killing 2 out of 5 newborns.

They try to solve racism...the "color" problem. When George wakes up, there are no colors. Everyone is grey. Our eyes never evolve to see colors. The different races are still there, however. And there are still wars. And killing.

The Future reshuffled as his change rippled forward, changing the past, until it reached the present.

Perhaps Daniel, due to the fact he was on the island, with the built-in time delay factor, was able to notice this.

ADDED LATER: In Flashes Before My Eyes, Desmond bought the ring and threw it off the bridge. Two things he did NOT do the first time around (according to Mrs Hawkings). But the acts weren't big enough to change the outcome (marrying Penny).

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charlie98210
"Whoa!" she said. "Cry 'Havoc!' And let loose the dogs of war!"
And, like Banquo's ghost, they just won't go away.