This is my own theory/timeline of Five Nights at Freddy's. It may not be that accurate but I don't want any haters. Also, in this theory, FNaF 2 is a prequel. You can send me your own theory or correct mine in the comments below!
Note: There is no Sister Location in this timeline. It would be too confusing for me.

First, there was Fredbear's Family Diner with Fredbear, Spring Bonnie, New Freddy, New Bonnie, New Chica, and New Foxy. One day, Fredbear bit a child's frontal lobe, known as the Bite of '87. New Foxy was blamed for the bite because he has sharp teeth. Anyways, Fredbear's Family Diner closed and Freddy Fazbear's Pizza opened.
    New Freddy, New Bonnie, New Chica, and New Foxy fell into severe disrepair and became "withered". They got replaced by Toy Freddy, Toy Bonnie, Toy Chica, and Toy Foxy. Children tore apart Toy Foxy, creating "Mangle". Eventually, the new Freddy Fazbear's Pizza closed its doors. The toy animatronics were scrapped due to possible malfunctions while the originals, which had fallen into severe disrepair, were being kept for possible future arrangements.
    Eventually, Freddy Fazbear's Pizza reopened and the company repaired Freddy, Bonnie, and Chica. They did not repair Foxy due to still being out of order, although, they did change his appearance a bit. One day, Purple Guy came and disguised himself with a golden Freddy costume and eventually lured five children to him. Then he murdered them one by one. He stuffed the children's dead bodies in the animatronics: Freddy, Bonnie, Chica, Foxy, and possibly Golden Freddy. They are set on a free roaming mode at night to prevent their servos from locking up but since they are possessed with the souls of the dead children, and because their murderer, Purple Guy, was a security guard at night, they mistake you for him. Plus, the rules for the company are that no endoskeleton can be left without a suit so the animatronics mistake you as an endoskeleton. One day, Purple Guy dismantled the animatronics, thus letting the souls of the dead children free. Purple Guy tries to hide from them in the only suit available, the Withered Spring Bonnie suit. He puts on the suit but it malfunctioned, thus killing Purple Guy, which became Springtrap. Freddy Fazbear's Pizza Closed its doors for good.
    Thirty years later, Fazbear's Fright: The Horror Attraction opened at the base of Freddy Fazbear's Pizza. The one day, the company discovered something in a dining area- a new animatronic. Somehow Purple Guy's nervous system connected to the animatronic parts and he came back to life as Springtrap. Anyways, the company brought him to the attraction! Before the company was able to open Fazbear's Fright, a fire erupted at it. It was probably caused by fataulty wiring. Anyways, Fazbear's Fright burned down and very little was salvaged, the pieces that were salvaged were sold at public auctions. Although, Springtrap did survive the fire.
                                                                                        The "End".