Each event described in this timeline is either depicted in the films (or on other artifacts such as newspapers depicted in the films), in the novels, in screenplays to the films, or described in interviews by the Bobs (director/co-writer Robert Zemeckis and producer/co-writer Bob Gale). Additionally, some dates (e.g. Verne's birthdate and Clara's birth year) are derived from episodes of the animated series, although whether or not that information is canon is subject to dispute by fans. Information from fan fiction is not included.
According to Doctor Emmett Brown in Back to the Future Part II, whenever a time-traveler alters key events occurring in the past, they effectively bring an alternate timeline into existence at their point-of-entry, and their original timeline is erased, even though its events are not forgotten by the time-traveler. Thus, every time travel jump into the past depicted in the Back to the Future saga "destroys" a current timeline and "creates" a new one, although Doc Brown often uses the phrase "erased from existence" to describe the deleterious effects of this process. Because of this, events from later timelines do not make their way backward into previous ones; for example, Bob Zemeckis has specifically denied the presence of a second Marty at Twin Pines Mall in Timeline 1.
As a time-traveler acquires multiple recollections of these altered timelines, a fourth-dimensional latticework begins to emerge which can be expressed graphically, as Doc Brown actually does for Marty McFly (in a crude chalkboard drawing) in Back to the Future Part II. Doc further explains that the new timeline causes the world to "change around" the time traveler (e.g. Jennifer and Einstein in 1985A), leaving him or her unaffected unless the new timeline precludes the time traveler's existence (e.g. Old Biff, in a scene deleted because, according to Bob Gale, the audience likely would not understand the reasoning behind it). Accordingly, there is no second version of the time traveler, as had been suggested by Imagineer Bob Gordon in issue #108 of Starlog Magazine, years before the second film was released.
Chart of alternate timelines
In the graphic above, the term Timeline 1 describes the original timeline. The blue stars represent the ensuing jumps by Doc’s DeLorean depicted in the trilogy. The resulting timelines, from 2 to 8, are represented by each successive horizontal arrow. Some Timelines, such as Timeline 5 in which the events of 1985A take place, are drastically different in terms of their respective events and effects. Accordingly, the events within each timeline are listed (chronologically) as they are understood to have occurred, but most often where they differ (often radically, or else subtly) from those of their "parent" timelines. For instance, permanently unaltered events in Timeline 1 during the 1960s are common to all BTTF timelines and are listed only once. Events that occur prior to a timeline split date are of course identical to those described in the lower-numbered timeline.
This is the original, unaltered timeline. In this timeline, Biff becomes George's boss and continues bullying him.
- Date unknown: Hill Valley is founded.
- Date Unknown: Buford Tannen is born.
- Dates unknown: The earliest of Doc's emergency money is printed.
- Seamus McFly, his wife Maggie McFly and his brother Martin emigrate from Ireland to the United States. They take a few years to get to California, shortly setting in Virginia City, Nevada along the way. Martin starts a bar fight there after someone calls him "yellow," and is stabbed to death as a result.
- April: William Sean McFly born, first son to Seamus and Maggie McFly and the first McFly born in America.
- Wednesday, September 2: Native American Horseback-archers are chased near Hill Valley by the United States Cavalry.
- Friday, September 4:
- Saturday, September 5: The Hill Valley Festival. As part of Hill Valley’s anniversary festivities, the new courthouse clock is started at exactly 8:00 p.m. PST. Photographs with the clock are offered to townspeople wishing to pose with the new timepiece. The clock will remain in faithful service to Hill Valley for the next seven decades.
- Date unknown: Marty's grandfather and George's father, Arthur McFly is born.
- Date unknown: Marty's grandmother and George's mother, Sylvia McFly is born.
- Date unknown: Marty's grandfather and Lorraine's father, Sam Baines, is born.
- Date unknown: Marty's grandmother and Lorraine's mother, Stella Baines, is born.
- Date unknown: Grays, the future publisher of Grays Sports Almanac, is founded.
- Date unknown: Toby Baines is born to Sam and Stella Baines.
- Date unknown: Sally Baines is born to Sam and Stella Baines.
- Date unknown: 12-year-old George McFly tries standing up for his friend Billy Stockhausen, but fails to do so.
- Date unknown: Old Man Peabody tries to breed pine trees on his farm. He has a twin pine.
- Saturday, November 5:
- Doc Brown slips off his toilet whilst hanging a clock and has a vision of the flux capacitor.
- Biff Tannen and his gang pick on George McFly at Lou's Cafe. Biff warns George never to go into Lou's Cafe again. Although Goldie Wilson urges George to stand up for himself, George ignores the advice.
- While spying on a girl (Lorraine Baines) changing through her window, George McFly slips and falls out of a tree into the street right in front of Sam Baines' car. After hitting him with the car, Baines takes him in, and his daughter Lorraine takes care of George. The two fall in love. 
- Monday, November 7: On the first day of school after George was hit by a car, Lorraine is infatuated with George as a result of the Florence Nightingale effect. With George recovering from an accident, Biff apparently leaves him (and Lorraine) alone for awhile. With his attentions focused on Lorraine, George stops writing science fiction stories and having missed Science Fiction Theatre on the 5th, apparently has no problem missing the show scheduled for Saturday the 12th.
- Tuesday, November 8: Biff and his gang stop by Lou's Cafe to make sure that George McFly isn't there, then drive off, perhaps commenting on a manure truck that is parked nearby.
- Saturday, November 12:
- Doc continues to think about the vision he had had a week earlier about the flux capacitor. If Doc is conducting an experiment, it is probably in his home rather than in Courthouse Square.
- Biff and his gang spend the evening drinking, but avoid going to the high school dance.
- Marvin Berry and the Starlighters play a music set, take a break at 9 o'clock, then resume playing music until the dance is over.
- George and Lorraine kiss for the first time at the Enchantment Under the Sea dance at Hill Valley High School. It is at that moment that Lorraine realizes that she is going to spend the rest of her life with George McFly.
- 10:04 p.m.: Lightning strikes the clock tower at precisely 10:04 p.m., damaging and stopping the seven-decade-old timepiece.
- Date unknown: The youngest Baines sibling is born to Sam and Stella Baines (name and sex are never mentioned, but Stella is very pregnant in November 1955).
- Date unknown: Lyon Estates, the future home of George and Lorraine McFly and their kids in 1985, is completed.
- Date unknown: George McFly and Lorraine Baines are married. Earliest possible time for them to move to Lyon Estates.
- 1976 – 1977
- Date unknown: Marty and Doc meet and become friends. According to the original Part I script, Doc shows up at Marty's house and hires Marty to sweep his garage in the year 1983. Doc gave Marty total access to his record collection, and they became friends.
- Sunday, May 22: Ronald Reagan announces he will run for a second term in office. Although a newspaper headline, seen in Timeline 2, mentions that Doc Brown is commended and wins an award, it is unknown whether this happened in the original timeline (because in 1985, Dr. Brown is described (by Mr. Strickland) as "a real nutcase").
- June: Linda McFly graduates in the Class of '84.
- Saturday, October 12: Libyan terrorists steal plutonium from the local power plant so Doc can build them a nuclear weapon. It is dismissed by the FBI as a "simple clerical error". 
- Friday, October 25:
- 8:18 a.m. Openings titles of "Back to the Future." All the clocks are set 25 minutes slow, displayed incorrectly as 7:53 a.m.
- 8:25 a.m. Doc asks Marty to meet him at Twin Pines Mall at 1:15 a.m. next morning.
- Marty arrives to school late then fails his audition with his band, The Pinheads, later after school.
- Marty admires a black Toyota 4x4 on the bed of a truck at the Texaco gas station.
- A woman asks Marty for a donation to preserve the non-functioning clock tower, handing him a flyer containing specific date and time details about the lightning strike to the clock. Marty puts the flyer in his pocket.
- Biff borrows George's car. He crashes it, and the two get into an argument about whether or not George knew about a blind spot.
- Lorraine's brother Joey fails to make parole again.
- Saturday, October 26:
- 12:28 a.m. Doc calls Marty to stop by at his garage to pick up his JVC camcorder.
- 1:16 a.m. Marty arrives at Twin Pines Mall.
- 1:18 a.m. Doc demonstrates Temporal Experiment #1.
- 1:20 a.m. Einstein becomes the first time traveler in the world by departing one minute into the future. (This time jump does not create a new timeline; timelines are only created by going back in time. Einstein merely moves 1 minute forward on Timeline 1. The Doc states this is the case with timelines in the blackboard scene in Part II.)
- 1:21 a.m. Einstein arrives at one minute into the future.
- 1:33 a.m. Doctor Emmett Lathrop "Doc" Brown is shot dead by Libyan terrorists.
- 1:35 a.m. Marty flees from the Libyans in the DeLorean and accidentally departs 1985 for 1955 by accelerating to 88 mph. His arrival there brings Timeline 2 into existence, and Timeline 1 fades from existence.
This is the timeline brought into existence by Marty's accidental time journey into 1955. It is the timeline that is current at the end of the first movie, before Doc takes Marty and Jennifer into 2015. In this timeline, George becomes an author and Biff becomes an auto detailer.
- Saturday, November 5:
- 6:15 a.m. Marty McFly arrives in 1955 from Timeline 1, on Old Man Peabody's farm, and knocks down one of Old Man Peabody's twin pine trees. After fleeing from an angry Old Man Peabody, Marty drives over to Lyon Estates, only to discover it under construction. Immediately after, the DeLorean gets depleted of plutonium, rendering it useless for time travel. Marty then hides it behind the Lyon Estates signboard, then makes it to Hill Valley on foot.
- 8:29 a.m. Marty arrives in downtown Hill Valley. He meets George McFly at Lou's Cafe, where he directly witnesses his future father's inability to stand up to Biff Tannen and his gang, even as Biff warns George not to come back into the cafe. Goldie Wilson gives George advice on standing up for himself, but George ignores it, even as Marty hints about Goldie running for Mayor (which inspires Goldie to go for it, much to the amusement of his boss, Lou Caruthers).
- Marty pushes George out of the way of Sam Baines's car and gets knocked unconscious, thus interfering with George's first meeting with Lorraine Baines. Lorraine then takes Marty in, then invites him to dinner with her family.
- Marty finds the young Doc Brown and shows him the time machine from thirty years in Doc’s future.
- Marty discovers the flyer with the details of the clock tower lightning strike. Doc has said that only "a bolt of lightning" could provide the power to
make the time machine function. The two devise a plan to channel the lightning exactly one week from this date.
- Sunday, November 6: Doc learns that Marty has interfered with his parents' first meeting and that he and his siblings will be “erased from existence” unless Marty can get them together.
- Monday, November 7: Marty, as "Calvin Klein", goes to Hill Valley High School to try and get George and Lorraine together, but she has developed a crush on Marty instead of George. Biff is not amused by this development.
- Tuesday, November 8:
- 1:21 a.m. Marty, in a radiation suit as "Darth Vader from the planet "Vulcan", visits George to try and make him take Lorraine to the dance that Saturday.
- George reports his weird alien experience to "Calvin," telling him that Darth Vader said he would melt his brain if he failed to ask out Lorraine. After George helps Marty open a Pepsi bottle, they go into the cafe, where George talks with Lorraine. The plan is successful at first, until Biff and his gang interfere. Biff and his gang chase Marty around Courthouse Square, and Marty improvises a skateboard to escape. Lorraine ignores George in favor of Marty, and asks Marty to the dance. Biff’s car has its first recorded encounter with a manure truck.
- Wednesday, November 9: George and Marty come up with a plan for Saturday night that will see George become a "fighter" for Lorraine Baines.
- Saturday, November 12:
- Biff, who is paying the $302.57 bill on his tidied-up car, boasts to Lorraine that he will marry her someday. She has just picked up her outfit for the dance at the frock shop, and rebuffs his advances: "I wouldn’t marry you if you had a million dollars". Biff jumps into his car to go home to get ready for the evening. There is nobody with him.
- Marty observes that Dave, and then Linda, have disappeared from his photograph from the future, indicating that the current timeline has already changed into a timeline in which they will never be born. He looks noticeably concerned.
- 9:00 p.m. Marty borrows Doc’s car to take Lorraine to the dance, but Biff steals her away. George arrives while Marty is suddenly absent. George punches Biff before he has his way with Lorraine, but she hasn’t fallen for him quite yet. George and Marty have more to do before Marty’s future is restored, and Marty’s photo proves it. Marty himself begins to be "erased from existence."
- 9:28 p.m. While George and Lorraine are finally beginning to enjoy themselves at the dance, Dixon cuts in. George nevertheless takes what is rightly his and the future Mr. & Mrs. McFly finally share their first kiss. The timeline in which George's and Lorraine's three children were never born has been averted, as Marty observes from his photo. Marty offers additional advice to his young parents in order to assure he will have a nice life back in '85. 
- 10:04 p.m. Lightning strikes the clocktower, and Marty travels back to 1985 in the time machine, via a complex utilization of the energy of the lightning strike itself devised by Doc Brown, and thanks to Marty McFly’s precise foreknowledge of this local historic event. There are no reported immediate witnesses to this event. Despite repeated attempts, the clock is never successfully repaired; in fact, some Hill Valley residents voice a desire for the clock’s preservation as is (along with the damaged ledge below it) to memorialize the unusual occurrence. Doc celebrates sending Marty back to the future.
- 10:05 p.m. The young Doc Brown returns home, unnoticed, having witnessed the earliest successful demonstration of time travel in human history. He is carrying a note Marty has handed him in lieu of verbal information about his own future, but is hesitant about reading it. While he has torn it up, he does not discard it. Doc must wait almost three decades before acquiring the technology required to build the device he has just seen with his own eyes, and is careful enough not to further interfere with McFly family events as they unfold over the next decades (see Timeline 1 above for these events, which are for the most part unaltered (although the McFly family is more affluent as a result of George being more assertive over the next 30 years); and will also occur as part of Timeline 7 below).
- Saturday, November 5:
- Thursday, March 15: George McFly wins an award for his writing.
- 1976 – 1977
- Date unknown: 8-year-old Marty accidentally sets fire to the living room rug. His parents do go easy on him in this timeline.
- Saturday, October 26:
- 1:24 a.m. Marty arrives from 1955. The rematerializing DeLorean fails to stop and crashes into the front of the Town Theater (now used for a Christian revival congregation). He then runs from the town square over to the Lone Pine Mall to witness the departure of his one-week-younger self, and finds out Doc survived because he was forewarned by the note Marty gave Doc just moments ago in 1955 about the Libyans (and that Doc finally had the courage to read in his long interim). (Doc and Marty drive the E. Brown Enterprises truck away from the parking lot at Lone Pine Mall before anyone comes to investigate the destruction of the Fotomat store by the Libyans' van). Doc retrieves the time machine from the Assembly of Christ building before any witnesses arrive downtown. No charges are lodged against driver or scientist.
- Doc takes Marty back to his home, and then travels with Einstein to 2015 on this timeline. As the Doc and his dog travel forward 30 years along this timeline, the next 30 years of timeline 2 are revealed below.
- 10:28 a.m. Marty awakes from a badly-needed night’s rest to discover he has a much-improved family life and circumstances, including ownership of a black Toyota four-by-four. His father also seems to have become an author (see below).
- Sunday, October 27: Marty races Needles and crashes into a Rolls-Royce, causing his future to be rotten (see entries below).
- October/November: George McFly's first novel, A Match Made in Space, is published. The cover alludes to young George, young Lorraine, and "Darth Vader" (Marty's anti-radiation suit, utilized as a costume in 1955).
- Saturday, October 26:
- Date unknown: Roberta Needles, older daughter of Douglas, is born.
- Date unknown: The Hill Valley Telegraph closes or sells its printing and news-gathering operations to USA Today to create a local edition of the nationwide newspaper.
- Date unknown: Invention of hover conversion, Mr. Fusion, the Black & Decker hydrator, hoverboards, power shoelaces and auto-drying jackets, skyways, rejuvenation clinics, suspended animation kennel, automated gas stations, automatic dog-walkers, portable thumb units, the multi-channel video screens, automated hovering news units (as used by USA Today), roll-down television sets (the McFly home runs The Scenery Channel on it in a window).
- Date unknown: The United States abolishes the trade of lawyers, allowing the justice system to move with far greater speed and efficiency.
- Date unknown: With the justice system operating more quickly and efficiently, the Clock Tower courthouse is converted into Hill Valley Courthouse Mall, complete with a glass center facade. Thanks to the continuing efforts of the Hill Valley Preservation Society, the 130-year-old clock remains stuck at 10:04 (along with the burnt lightning rod above it and the damaged ledge below it).
- Date unknown: The US Weather Service develops the ability to either end or predict the end of rainfall to the exact second.
- Date unknown: Relations with Vietnam improve and now there are promotions to surf there.
- Date unknown: Pepsi introduces Pepsi Perfect, a vitamin enriched cola (Marty orders this from the video waiter at the Cafe 80's).
- Date unknown: Pizza Hut introduces the dehydrated pizza that Lorraine McFly cooks in the hydrator.
- 2009 or 2013
- Date unknown: A woman becomes President of the United States (she is mentioned in the 2015 newspaper).
- Doc spends an unknown amount of time in 2015 and later. While he's there, he places Einstein in a suspended animation kennel, outfits the time machine with a Mr. Fusion and a hover conversion, undergoes personal rejuvenation surgery, and learns as much as he can about Marty Jr.'s meeting with Griff on the 21st. Eventually, Doc leaves for 1985 to fetch Marty and Jennifer. This creates Timeline 3 which begins at the Doc's entry point of 1985 and timeline 2 fades away.
- Date unknown: Jaws 19 debuts at the theater: this time, it's really really personal.
- Wednesday, October 21:
- Thursday, October 22: Marty Jr. is tried, convicted and sentenced to 15 years in jail for a robbery.
- Friday, October 23: Queen Diana visits Washington according to the 2015 newspaper.
- Wednesday, October 28: Marlene McFly attempts to break her brother out of prison. She is sentenced to 20 years in jail.
This is the timeline which Doc brings into existence by traveling to 1985 to seek Marty and Jennifer's help. In this timeline, the fate of the McFly children ought to have been greatly improved. Unfortunately, "Old" Biff's stealing the DeLorean and traveling back to 1955 retroactively changes the events of this timeline and bring Timeline 4 into existence instead. Biff quickly returns the DeLorean to 2015 undetected (before any past alterations have taken place), and Doc, Marty and Jennifer depart moments before it fades away. It is implied that Doc would bring both Marty and Jennifer back to 1985 after the future excursion, due to their future selves still existing and appropriately aged in 2015.
- Saturday, October 26:
- Doc returns from 2015, sans Einstein, and crashes the DeLorean into the garbage cans in the McFlys' driveway. Doc then informs Marty that "something has got to be done about (his) kids." Doc then proceeds to take Marty (and Jennifer by circumstance) forward along this new timeline to 2015.
- Biff Tannen, wanting to show Marty the matchbooks he had printed for his auto detailing business, witnesses the DeLorean hovering briefly before taking off for the future. He will remember this for the next 30 years.
- Saturday, October 26:
- Wednesday, October 21:
- 4:29 p.m.Doc, Marty and Jennifer arrive in 2015 to save Marty Jr. from Griff. Marty poses as Marty Jr. and turns down Griff's proposal. After the hoverboard chase which ensues, only Griff and his gang are arrested for damaging the courthouse. At some point Marty acquires a Grays Sports Almanac with the intention of using it to his advantage once he returns to his own decade.
- Doc returns to pick up Marty, having retrieved Einstein from his suspended animation kennel, and witnesses Marty's success in changing his family's future, as indicated on his newspaper changing due to the ripple effect.
- Old Biff, age 78, who has been waiting for this opportunity for three decades, steals the DeLorean and heads back to 1955 with Marty’s sports almanac, which Doc angrily threw into a convenient trash receptacle, bringing Timeline 4 into existence six decades in the past.
- Jennifer, rendered unconscious due to her unnecessity in saving Marty Jr., is taken to her future home. There, she hides in a closet and witnesses Marty's future family life. She witnesses Marty getting fired from his job and receives a fax about it. She attempts to escape the house, but encounters her 2015 counterpart and faints. Doc takes her out of the house safely.
- Biff returns the DeLorean to 2015 shortly thereafter without Doc and Marty immediately noticing. He is able to do this because his younger self is not immediately able to act on the knowledge contained in the almanac, so the past remains unchanged until 1958 arrives. However, Timeline 4 has been brought into existence between the time Biff leaves 1955 and returns to 2015, and he either collapses from fatigue or fades from existence after having been presumably murdered by Lorraine in 1996. (see below)
- 7:28 p.m. Doc, Marty, Einstein and Jennifer depart 2015 for the "alternate 1985", bringing Timeline 5 into existence.
- Date unknown: Doc returns to the suspended animation kennel to retrieve Einstein.
- Wednesday, October 21:
This is the timeline Old Biff brings into existence in 1955 by arriving from 2015 in the stolen DeLorean, almanac in hand. It is replaced with a virtually identical Timeline 5 on October 26, 1985 when Doc, Marty, Einstein and Jennifer arrive from 2015, and observe the damage Biff has accomplished.
- Saturday, November 12:
- The 78-year-old Biff Tannen arrives from 2015 sometime that morning with Gray’s Almanac. He hides the DeLorean in an undetermined location and sets out to find his younger self, who has just survived an automotive encounter with a manure truck, creating a lasting memory. Young Biff will have to pick up the car this morning downtown, as old Biff recalls correctly.
- Young Biff boasts to Lorraine that he will marry her someday. She has just picked up her outfit for the dance at the frock shop nearby, and rebuffs his advances. Biff is about to jump into his car to go home to get ready for the evening, when he encounters an elderly stranger occupying the driver’s seat. The stranger soon informs him, "Today’s your lucky day."
- Old Biff, entirely in secret, demonstrates the power of the almanac and convinces his younger self to hold on to it: "Keep it in a safe". He also informs him to kill anyone who has knowledge about the almanac, specifically "some kid" or "a crazy, wild-eyed old man who claims to be a scientist" (referring to Marty and Doc, respectively).
- 6:38 p.m. Old Biff departs 1955 to return the DeLorean undetected, not realizing his younger self might eventually lose the almanac. Doc Brown will fail to notice Old Biff’s departure time on the time readouts in the DeLorean, having distracted himself with thoughts of women and the old West.
- Saturday, November 12:
- Wednesday, October 14: Biff Tannen wins another large sum of money at a sports event. He is seen smiling on the cover page of the next day's edition of the newspaper, with the almanac partially visible in his pocket.
- Date unknown: Biff Tannen wins again and again, gaining the nickname, "The Luckiest Man On Earth."
- Thursday, March 15: George McFly is shot dead by Biff Tannen on his way to pick up his writing award. He was against BiffCo's policies.
- Date unknown: Biff Tannen marries Lorraine McFly and becomes stepfather to Dave, Linda and Marty McFly, shipping Marty off to boarding schools overseas. Match, Skinhead and 3-D are still Biff's cronies.
- Date unknown: Biff Tannen's lobbying is successful as the state of California (or perhaps all of the United States) legalizes gambling.
- Date unknown:The Clock Tower, described as "Hill Valley's dilapitated courthouse", is re-built as Biff's Pleasure Paradise Hotel and Casino.
- Date unknown: Hill Valley High School is burnt down.
- Date unknown: Something causes Biff's death, but exact details are unknown. A theory suggested by the Bobs says that Lorraine found out Biff had killed George, and shot him out of revenge. This would seem to have the effect of erasing Old Biff from existence in 2015, as depicted in a scene deleted from BTTF Part II.
This is the alternate timeline brought into existence when Marty, Doc, Jennifer and Einstein return from 2015. This is referred to by Doc as 1985A, which is depicted in BTTF Part II. The key difference between this timeline and Timeline 4 is the simultaneous presence of two Martys (his doppelganger overseas at boarding school), two Docs (his doppelganger committed to a mental institution and unable to invent the time machine) and the alternate Einstein and Jennifer, the latter whom is still unconscious from what she has witnessed in 2015 (their 1985A doppelgangers, if they have any, are never seen or mentioned).
- Saturday, October 26:
- 9:00 p.m. Doc, Marty, Einstein and Jennifer arrive back from 2015 and find out things have radically changed (see Timeline 4 above). Marty is caught by Match, Skinhead and 3-D, meets the radically alternate 1985 versions of his mother, brother Dave, and Biff Tannen, and is a direct witness to Biff’s way with women.
- Sunday, October 27: Doc deduces what has happened in the past with Biff and the almanac from the evidence Biff has carelessly left behind, but he has no way of knowing when and where the transfer occurred. A courageous Marty confronts Biff about his secret document and easily extracts the needed information from the smug mogul. Biff, recalling the advice given by his future self, grabs his gun to kill Marty. A chase with Match, Skinhead and 3-D naturally ensues, and Marty escapes once again after learning it was Biff who murdered his father.
- 2:42 a.m.Doc and Marty head back to 1955 to put the history they remember back on track. Jennifer Parker and Einstein are left behind, as Doc surmises that they will not be erased when 1985A is. At this point, Timeline 5 fades away, to be replaced by the nascent Timeline 6.
- Saturday, October 26:
This is the key timeline brought into existence when Doc and Marty arrive in 1955 to relieve Biff of his newly acquired almanac from the future, thus preventing Timeline 4 and Timeline 5 from coming into existence, but without disturbing Timeline 2 as Marty has previously accomplished. This is the timeline that is depicted in the "1955" part of Back to the Future Part II. For purposes of clarification, this timeline can be thought of as a "patched" version of Timeline 2, with double Docs and Martys. It bears noting that for several hours during this day, three instances of Doc’s DeLorean are present in Hill Valley simultaneously.
- Saturday, November 12:
- 6:00 a.m. Doc and Marty arrive from Timeline 5 in a DeLorean technologically improved than the one (with depleted plutonium) in which the younger Marty has already arrived (Timeline 2). They have left Einstein at Doc's garage and Jennifer Parker safely asleep at home in 1985-A, as Doc surmises that they will not be erased by any changes to the future that they will make. He also advises Marty that Biff’s initial acquisition of the almanac must not be interfered with, so that Old Biff will return the time machine to 2015 thinking he’s succeeded.
- Morning: Old Biff arrives (in yet another instance of the DeLorean) to transfer the almanac to his younger self. He locates Biff downtown.
- Young Biff Tannen boasts to Lorraine that he will marry her someday. She has just picked up her outfit for the dance at the frock shop, and rebuffs his advances. As this goes on, Marty smuggles himself into the back of Biff's car. Biff is about to jump into his car to go home to get ready for the evening, when he encounters an elderly stranger occupying the driver’s seat. The stranger says he has a way for Biff to eventually get Lorraine to the altar. Young Biff fails to recognize his older self, even though he’s mysteriously able to start Biff’s car.
- Marty McFly is an intimate witness to Old Biff’s demonstration of the power of the almanac, but he does not interfere, as Doc has advised. Young Biff tells his older self he’ll "...take a look at it."
- 6:38 p.m.: Thinking he’s done enough to change the future, and intending to escape detection, Old Biff departs in the DeLorean to the same moment he departed in 2015 (see Timeline 3).
- 9:28 p.m. Marty retrieves the Sports Almanac from an unconscious Biff, while Doc departs the Lyon Estates construction site to fly towards the roof of Hill Valley High School.
- A more mature and foreknowledgeable Marty fights off Match, Skinhead and 3-D and keeps them from jumping the naive Marty (from Timeline 2), allowing the events of that timeline to occur as they had before (i.e., as Marty recalls it from his point of view). Marty avoids any direct contact with his day younger self, until he loses the almanac to Biff again.
- After much wasted time and effort, Marty ultimately retrieves the almanac from Biff’s car. Biff, who has not paid for the $300 repairs after his first wreck, crashes his '46 Ford a second time, an event that had not happened in any previous timeline. Burning the almanac causes this timeline to fade back to closely match Timeline 3, making Old Biff's visit to the past mostly inconsequential, except for Biff's extra encounters with Marty. Marty and Doc are able to visually confirm the erasure of 1985A from items they’ve retrieved from that alternate future.
- 9:44 p.m. The hover-converted DeLorean from 2015 and 1985-A, with Doc on board, gets unexpectedly struck by lightning just outside Lyon Estates and sent back to January 1, 1885 due to an on-board malfunction Doc neglected to correct. This brings Timeline 7 into existence, seven decades further in the past. 
- Saturday, November 12:
This is the timeline Doc and Marty exist in, separated by 7 decades of time, at the end of Back to the Future Part II and the beginning of Part III (before Marty’s trip back to 1885). It is a timeline in which Doc lives in 1885, without Marty, for only eight months and almost seven days, and is shot by Buford Tannen.
Because of Doc's unintended trip to 1885, there are four DeLorean time machines that exist on November 12, 1955 in this timeline, because this is a timeline where a DeLorean has been stored in a mine for more than 70 years. Even as 1955 Doc is planning to send DeLorean "A" back to the future, 2015 Biff has brought DeLorean "B" with an almanac inside, and 1985 Doc and Marty have brought DeLorean "C" to retrieve the almanac -- there is DeLorean "D" inside the Delgado Mine.
- Thursday, January 1
- Date unknown between January 1 and September 3: Blacksmith Emmett Brown is hired by Buford Tannen to shoe Buford's horse, but is not paid. After getting thrown off his horse and breaking a bottle of whiskey, Buford blames Doc for the accident and demands a total of eighty dollars from him; five dollars for the whiskey and seventy-five dollars for the horse, which was shot.
- Saturday, July 4: Doc passes out after drinking one shot of whiskey at the 4th of July celebrations.
- Saturday, August 29: There is a meeting of the townspeople over who will pick up the new schoolteacher on September 4. Doc volunteers.
- Tuesday, September 1: Doc buries the broken DeLorean time machine in the Delgado Mine. He writes a letter to be delivered personally by Western Union to Marty McFly on November 12, 1955 exactly at 9:45 p.m. to the exact stretch of road he was hovering above when he was struck by lightning.
- Friday, September 4: Doc picks up Clara Clayton. It is love at first sight. Unknowingly, Doc also prevents Clara's death that day, and Shonash Ravine is never renamed Clayton Ravine in her memory.
- Saturday, September 5: The Hill Valley Festival. A photographer takes a portrait of Doc posing next to the new courthouse clock (this photo is discovered by Marty and young Doc in 1955 at the library). While Doc dances with Clara, Buford Tannen shoots Doc in the back because he never paid Buford the eighty dollars.
- Monday, September 7: Doc dies of the bullet wound Tannen caused, and is buried in Boot Hill Cemetery.
- Saturday, November 12:
- In this point of the timeline there are now four instances of the DeLorean present simultaneously (the one Marty brought here to create Timeline 2, the one Biff brought here to create Timeline 4, the one Doc and Marty brought to create Timeline 6, and finally the one that Doc hid in the mine in the past after he created Timeline 7)
- 9:45 p.m. A vehicle driven by a Western Union agent arrives at the entrance to Lyon Estates. The agent delivers to Marty, on time at that specified location, in the pouring rain, the letter Doc dispatched in 1885. (This event in Timeline 6 is created by a ripple effect transforming Timeline 6 into Timeline 7)
- 10:05 p.m. Lightning having just struck the clocktower, Marty scares the young Doc by "returning" on foot seconds after Doc sent the younger Marty back to the future, in effect creating an unexpected closed loop (from the young Doc’s point of view). Doc utters "Great Scott!" and suddenly faints. Marty drives the unconscious Doc back to his house in Doc's car.
- Sunday, November 13:
- 7:01 a.m.: Young Doc reads the soggy old letter his 30-year-older self wrote seventy years in the past.
- Monday, November 14: Marty and Doc uncover the DeLorean with repair instructions and his walkie talkie from the Delgado Mine near Boot Hill Cemetery, where the older Doc Brown was buried in 1885. As fate would have it, they also find Doc's grave and learn about Buford Tannen. They elect to photograph the headstone, as it will serve as a "ripple-effect" indicator of Marty’s success in 1885.
- Marty insists on going back to 1885 to rescue his friend.
- Tuesday, November 15: Doc repairs and "soups up" the unearthed DeLorean, using tubes as well as early transistors to provide time-travel capability. He also installs fresh oversized batteries on the walkie talkies.
- Wednesday, November 16
- 10:00 a.m. Marty leaves 1955 and heads back to 1885 to rescue Doc. This act initiates the ultimate timeline, Timeline 8. Young Doc is left behind in this timeline undisturbed to wait a few decades until the DeLorean is built, and avoids further contact with the McFlys until the 1980s as outlined above (Timeline 1 and Timeline 2). 
- Saturday, November 12:
This timeline comes into existence when Marty arrives in 1885, to try to prevent the events that led to Doc's death in Timeline 7 at the hands of Buford Tannen. It is this timeline in which Doc and Marty appear for most of Back to the Future Part III. It is also the final timeline depicted in the trilogy, as the DeLorean will no longer travel backwards in time. Since Marty chooses not to race Needles upon his return to 1985, the future is changed once again, and the alternate futures Doc and Marty have experienced in Timeline 2 and Timeline 3 are erased by this timeline. Note: Two DeLoreans exist in this timeline for five days in 1885, from September 2nd when Marty arrived, until September 7th when he departed for 1985.
- Wednesday, September 2:
- 8:00 a.m. Marty McFly arrives in 1885 to rescue Doc from impending doom. Native American Horseback-archers, who were on the run of the Federal Forces, shoot the fuel line in the time machine, leaving the DeLorean with no fuel at all. He later meets his ancestors Seamus, Maggie, and William McFly on the McFly farm and assumes the name "Clint Eastwood".
- Thursday, September 3: Marty runs into Buford "Mad Dog" Tannen, great grandfather of Biff Tannen, and upsets him, causing Tannen to nearly hang Marty. Doc saves Marty in time. Marty informs Doc of his impending death involving Clara Clayton and Buford Tannen. Aware that he will fall in love with Clara Clayton and worried about changing his future, Doc decides not to pick her up, as he has already volunteered to do five days ago.
- Friday, September 4: Doc tries repairing the DeLorean, and accidentally saves the life of schoolteacher Clara Clayton. It is love at first sight.
- Saturday, September 5: The Hill Valley Festival. Doc and Marty have a photograph taken, posing next to the new courthouse clock (this photo is given to Marty in 1985 by Doc at the spot where the DeLorean was destroyed by a locomotive near Eastwood Ravine). While Doc and Clara dance, Buford Tannen tries to shoot Doc, but Marty interferes and saves him.
- Sunday, September 6:
- 7:00 a.m. Marty wakes up. After being confronted by Doc about the dangers of fighting Buford, Marty checks his photograph from 1955, and gets a shock. The future of timeline 8 in which Doc is killed is replaced by one in which Marty, aka "Clint Eastwood", is likely to be killed. Doc and Marty prepare to go back to the future. Doc says goodbye to Clara and tells her the truth, but she doesn't believe him. Both are broken-hearted; she prepares to leave Hill Valley and he goes to a saloon. Buford and his gang rob the Pine City stage.
- Monday, September 7:
- 8:00 a.m.Marty has a showdown scheduled with Tannen; Marty and Doc are ready to escape through the back door when Tannen calls Marty "yellow". Marty still decides not to face Tannen, showing an incredible amount of growth from a mere day earlier, and is about to walk away when Tannen's gang gets a hold of Doc and threatens to shoot him.
- Marty then decides to face Tannen, and survives due to a trick learned from the Clint Eastwood movie A Fistful of Dollars (which was being watched by Biff in 1985A, in timeline 5). Again Marty checks the photo he has brought, and is relieved. The future of timeline 8 in which Marty is killed is replaced by one in which both Doc and Marty survive.
- Tannen and his gang are arrested for the robbery of the Pine City stage.
- Meanwhile, Clara Clayton, on a train bound for San Francisco, overhears a passenger talking about the heartsick Doc Brown; her belief restored, she stops the train and jumps off to find Doc. She discovers clues at the blacksmith shop and rides on horseback towards the spur line Doc and Marty are using. She must reach Doc before he vanishes forever.
- Doc and Marty are using a hijacked train's locomotive to push the DeLorean up to 88 mph toward Shonash Ravine so they may both go back to the future (1985). Marty succeeds in doing so, but Doc, who has gone to Clara's rescue on the accelerating locomotive, and Clara are forced to stay behind. Doc now has the hoverboard and one of the walkie talkies. Since "Clint" was observed stealing the engine, and is presumed to have gone down with it, he enters the town's folklore as the man who beat Mad Dog Tannen, and Shonash Ravine is renamed Eastwood Ravine.
- 9:00 a.m. Marty departs 1885 and finally returns to 1985.
- Tuesday, December 15: Doc and Clara are married. 
- Wednesday, September 2:
- Sunday, October 27:
- 11:00 a.m.Marty McFly returns from 1885 and the stopped DeLorean is almost immediately demolished head-on by a diesel locomotive approaching the Eastwood Ravine Bridge in the opposite direction. Marty escapes. He returns home to see everything is back to normal (as per Timeline 2). He then drives over to check on his sleeping sweetheart. She is just as Doc predicted.
- In a virtuosic display of uncharacteristic self-restraint, Marty decides not to race Needles, and avoids crashing into a Rolls Royce, thus erasing the future experienced in Timeline 2. Jennifer surprises Marty with the fax she retrieved from 2015 in that very timeline, and as it "ripples" into a blank sheet of paper, she discovers the hidden truth about time travel, exclaiming: “It erased!” Marty takes her to see the remains of the DeLorean.
- Doc, Clara and their sons arrive at Marty’s crash site in their time locomotive to briefly check up on Marty and Jennifer, and to retrieve Doc's dog, Einstein, who was not erased by the timeline as Doc predicted. Jennifer and Marty show Doc the blank fax, and he dispenses some sound advice about its significance. The Brown family departs for times and places unknown.
- Sunday, October 27:
- Date unknown: Doc, Clara and the kids hover convert their train time machine and make additional upgrades.
Behind the scenes
- Doc says that 1947 was when suitable replacement parts for the time circuit control microchip would be invented. This was also the same year of the famous Roswell, New Mexico alien crash landing incident (it was also the year when the transistor was invented).
- Doc states that components that would be usable for the DeLorean would not be invented until various times in the 20th century. However, the Time Train has a working flux capacitor and time circuits, even as it was built sometime around 1895, presumably with parts used from the hoverboard and walkie talkie he had after saving Clara from falling from the train.
Notes and references
- ↑ 1.0 1.1 Robert Zemeckis and Bob Gale, Q&A, Back to the Future [DVD], recorded at the University of Southern California
- ↑ Template:Cite magazine
- ↑ Back to the Future Part II: The money was visible in Doc's suitcase.
- ↑ Historical fact. See From the Earth to the Moon for details. The book is mentioned in Back to the Future Part III.
- ↑ based on an 1885 issue of the Hill Valley Telegraph that commemorates the 20th anniversary of the event
- ↑ Clara mentions this in conversation with Doc in Back to the Future Part III
- ↑ Historical fact. See Twenty Thousand Leagues Under the Sea for details. The book is mentioned in Back to the Future Part III.
- ↑ Back to the Future Part II: Doc and Marty read the newspaper in 1955.
- ↑ Back to the Future Part III: The clock was seen in the background at the train station in 1885.
- ↑ Back to the Future Part III: Marty McFly tells the tale to Doc in 1885.
- ↑ Back to the Future Part III: A sign reading "scheduled completion summer 1886" can be seen next to the unfinished bridge in 1885.
- ↑ 12.0 12.1 Back to the Future Part III: Doc tells Marty about it in 1955.
- ↑ based on a mention in the BTTF novel that in 1985, Doc is 65 years old.
- ↑ Historical fact. See Clint Eastwood for details.
- ↑ as established in Back to the Future Part II, which recounts Biff's life story and "how a trip to the races on his 21st birthday made him a millionaire overnight," and shows a newspaper dated March 27, 1958
- ↑ as seen on George's tombstone in 1985A in Back to the Future Part II; names of parents are from the BTTF novel at page 91
- ↑ from DVD commentary by Bob Gale in Back to the Future
- ↑ Historical fact. See Calvin Klein for details.
- ↑ 19.0 19.1 19.2 Back to the Future Part III: Part of Doc's letter.
- ↑ Back to the Future. Doc tells Marty about this in the parking lot of Twin Pine Mall in 1985, and the farm is seen when Marty gets in 1955.
- ↑ 21.0 21.1 Back to the Future Part I. Doc tells Marty about this in the parking lot of Twin Pine Mall in 1985.
- ↑ Back to the Future. Lorraine tells her kids part of this story in 1985. The rest is witnessed by Marty in 1955.
- ↑ Historical fact. See history of Toyota for details.
- ↑ Historical fact. See Johnny B. Goode for details.
- ↑ 25.0 25.1 25.2 25.3 Back to the Future Part II. Mentioned in the video presentation on the life of Biff in the Biff Tannen museum, in the alternate 1985.
- ↑ 26.0 26.1 Back to the Future Part I. According to newspaper clippings framed on the wall of Doc's house.
- ↑ Historical fact. See Tab (soft drink) for details.
- ↑ Historical fact. See Studebaker's exit from the auto business for details.
- ↑ Historical fact. See A Fistful of Dollars for details. The film is depicted in Back to the Future Part II and homaged in Back to the Future Part III.
- ↑ Bob Gale referred to the date in a draft screenplay for Part II, although this did not end up in the film trilogy, the novelizations, or the animated series
- ↑ from Back to the Future
- ↑ Historical fact. See Caffeine-Free Pepsi for details.
- ↑ Back to the Future. According to a TV news program heard in the background.
- ↑ The timestamp can be evidenced in Back to the Future II while Doc is heading towards the high school roof.
- ↑ 35.0 35.1 35.2 Back to the Future Part II. According to a newspaper Doc showed to Marty.
- ↑ Page 42 of the Back to the Future part III novel shows the Last Time Departed display as 9:44 pm while Doc prepares to send the DeLorean to Sept. 2 1885.
- ↑ 10 AM is the time given in page 41 of the Back to the Future III novelization
- ↑ from the animated episode, Solar Sailors; Doc and Clara are celebrating their anniversary on December 15, 1991, and Doc jokes that they've been married almost 106 years.
- ↑ conjecture from Jules being two years older than Verne, and apparently being about 9 years old when the family first leaves 1895, and conceived after his parents' marriage
- ↑ from the animated episode, "By Any Other Name"
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