Before Cedric Diggory can use a Transfiguration spell to change a rock into a dog, the two boys use a Disarming Charm to stop him. He fails the task. After 5 minutes, the two boys are flung back to 3 September, 2020 to find they have changed the future in this timeline.
When Albus Potter and Scorpius Malfoy travel to the second task in February 1995, they do not change the events of their most recent visit to 24 November 1994. Therefore, Cedric still fails the first task in this changed timeline.
Even though Cedric completed the first task, it still didn't not happen in the original timeline since Scorpius has yet to correct the second task. Once he did, the fourth timeline was ended and the original timeline was restored.
The Yule Ball of the Triwizard Tournament is held. Hermione Granger, having seen two Durmstrang students disarming Cedric Diggory, suspects that Viktor Krum told them to sabotage Cedric's First Task, and turns him down. She goes with Ron Weasley. However, at the ball, Ron Weasley dances with Padma Patil and the two fall in love.
The Yule Ball of the Triwizard Tournament is held. Ron Weasley goes with Padma Patil and Hermione Granger goes with Viktor Krum. Without realising, seeing this sparks jealousy in Ron Weasley, which later leads to him and Hermione Granger falling in love. It is the same as the second timeline since Scorpius is yet to change his intervention in the first task.
Scorpius Malfoy, Hermione Granger, Ronald Weasley and Severus Snape time travel from the third timeline and use a Shield Charm to fix their intervening in the first task. It changes the future to a fifth timeline where the day of the Yule Ball happened the same way it did in the original timeline, although since they still haven't fixed their intervening in the second task, it is not completely the same. They eventually do and the original timeline is restored.
↑Harry Potter and the Prisoner of Azkaban, Chapter 12 (The Patronus) "We should be starting this week; he said he’d have time after Christmas". The statement was made when "the rest of the school returned shortly after New Year"
↑Harry Potter and the Prisoner of Azkaban, Chapter 21 (Hermione's Secret) It happens the same day Buckbeak would be executed. It was stated he "shall be executed on the sixth of June at sundown –" so the other events happen on the same day
↑Harry Potter and the Goblet of Fire, Chapter 14 (The Unforgivable Curses) (Page 224), Hermione says she's set up S.P.E.W. Harry Potter and the Goblet of Fire, Chapter 15 (Beauxbatons and Durmstrang) (Page 228), begins "Early next morning". It's the same day that a notice for the Triwizard Tournament goes up (Page 235), stating that students of "Beauxbatons and Durmstrang will be arriving... on Friday the 30th of October". Another student states it is "only a week away!" which makes the date the notice went up the 23 October and the date Hermione announces S.P.E.W the 22 October
↑Harry Potter and the Half-Blood Prince, Chapter 11 (Hermione's Helping Hand) states "Jimmy Peakes, a short but broad-chested third-year boy". Since the book takes place in the 1996-1997 school year, Jimmy could only have started in the 1994-1995 school year