1866 was a year in the 19th century.
- Eleven-year-old Clara Clayton comes down with diphtheria and is quarantined for three months.
- Clara's father places a telescope next to her bed for her to use, which sparks her lifelong interest in astronomy and science.
First altered timeline
- Thursday, October 25: Marty McFly arrives from 1855 to meet 11 year old Clara Clayton, Marty found Clara at her bedroom, and says happy birthday to Clara. Clara was like "Who are you?", Marty says "I'm Marty McFly from the future." Clara asks him "What year did you come from?" and Marty says "I'm from the year 2025, that's in the 21st century." Marty shows her the time machine, Marty teaches her everything about how time travel works. After that Clara wants to come to the future as well. Marty thought of a good idea, he thinks Clara wants to see the future, so Marty agrees to take her with him. Marty helps her fuel up the Mr. Fusion with garbage, Marty shows her the time circuits and teaches her how to put the destination time on the keypad. 11 year old Clara wants to go back to the 21st century. So Marty agrees and tells her about the future, so they depart 1866 for 2025 and Clara's house changes into Clara's Indigenous House. That means this timeline fades from existence bringing the Indigenous timeline into existence.
Second altered timeline
- Friday, October 26: Marty and Clara arrive from 1785, Marty takes Clara back home, Clara says "Goodbye and thank you." Marty says "Your Welcome." and Clara wants to fuel up the Fusion Generator one last time, Marty agrees, She fuels up the fusion generator with some garbage, and Marty thanks her for fuelling up the DeLorean and Marty departs 1866C (Aboriginal 1866) for 2025E (Aboriginal 2025). Clara goes inside the house to tell her parents her story with Marty McFly. But the house has now became a indigenous house, then she found her parents, she bravely tells them her story. After that Clara's mom and dad gets her to sleep.
- Saturday, October 27: Marty McFly arrives from 2025E (Aboriginal 2025) to pick up 11 year old Clara Clayton, Clara wakes up and runs outside Marty and Clara both realised that something happened on Christmas in 1785 must have changed the alteration of time, Marty tells Clara all about the future, Clara was amazed, so she joined in and tells her parents about the future. Marty and 11 year old Clara fuel up the Fusion Generator, they jumped into the DeLorean, Clara sets the destination time to December 25th 1785 4:00 AM, then they depart 1866C (Aboriginal 1866) for 1785 a fire trail has been left behind. Timeline 2 fades from existence, bringing Timeline 3 into existence.
Third altered timeline
- Saturday, October 27: Marty and Clara arrives back from 1785, Marty takes Clara home, when they got there, Clara's house is back to normal, Marty drops Clara off, Clara fuels up the Fusion Generator, Marty hops in the car and departs 1866 for 2025. Clara goes inside her normal home to tell her parents her story.
- Monday, November 12: Marty McFly returns from 2025 to pick up Clara Clayton, Marty tells 11 year old Clara that his future has turned into the Western Futuristic Technology, it now has robotic-hover-horses, Western-Hover-Time Machines, Hover-Carriages and Western versions of the Hoverboards. Clara found-out in 1785, in December 26th on 11:00 AM, The Time Police arrested Vicky Clayton from using the Heirloom Brass Clock. So Marty and Clara have to go back and save Vicky Clayton from the Time Police, Clara fuels up the Fusion Generator, Marty and Clara hop in the DeLorean, Clara sets the Destination Time to December 26th 1785 10:55 AM, then she decided to set it to December 26th 1785 10:42 AM instead, Marty thinks its a good idea to save Vicky Clayton early from the Time Police, Marty switches the DeLorean into Hover mode, they accelerate the Flying DeLorean up to 88mph, they depart 1866 back to 1785 to save Vicky Clayton. Timeline 3 fades from existence, bringing Timeline 4 into existences.
Fourth altered timeline
- Monday, November 12: Marty and Clara returns from 1785, Marty checks the newspaper and the wanted poster, they changed from Vicky Clayton to Buford Tannen. Marty and Clara completed their rescue mission. Marty drops Clara off back to Clara's home, Clara fuels up the Fusion Generator one last time, Clara gives Marty a hug, Clara tells Marty she'll see him in 1885, Marty will see her there too, Clara closes the door, Marty switches the DeLorean back to Hover mode, and accelerates the Flying DeLorean up to 88mph, disappearing through time back to 2025, Clara goes inside her home to tell her parents her story.
- Tuesday, November 13: A 30 year old Clara Clayton arrives in her own time machine to meet her 11 year old self. Suddenly Marty McFly arrives from 2025, Clara fuels up the fusion generator, Marty sets the destination time to April 3rd 0033 12:00. They Depart 1866 back to 33AD.