The Butterfly Effect(2004)

Evan Treborn has lost track of time. From an early age, crucial moments of his life have disappeared into a black hole of forgetting, his boyhood marred by a series of terrifying events he can't remember. What remains is the ghost of memory and the broken lives around him--the lives of his childhood friends, Kayleigh, Lenny and Tommy. Throughout his childhood, Evan was under the care of a psychologist who encouraged him to keep a journal, detailing the events of his day-to-day life. Now in college, Evan reads from one of his journals and finds himself thrust suddenly, inexplicably back in time. He comes to realize that the notebooks he keeps under his bed are a vehicle by which he can return to the past and reclaim his memories. But these recollections only leave Evan feeling responsible for the damaged lives of his friends, most crucially that of Kayleigh, his childhood sweetheart who he continued to love into adulthood.Determined to do something now that he was incapable of doing then, Evan purposely travels back in time, his present-day mind occupying his childhood body, in an attempt to re-write history and spare his friends and loved ones these traumatic experiences.