"Is it Dark Magic or is it something else entirely - Cedric Diggory is disarmed…."
-- Ludo Bagman (CC2.7)
24 November 1994
They hear the introduction and announcements of Ludo Bagman and encounter a suspicious Hermione Granger (who Scorpius intially mistakes her for her daughter Rose). When Cedric Diggory makes his attempt to take the golden dragon’s egg from the Swedish Short-Snout, Albus uses his wand to disarm Cedric (CC2.7).
Scorpius and Albus are then transported back to the present by a malfunctioning Time-Turner and discovered by their parents in the Forbidden Forest (CC2.7).
Initially during the First Task of the Triwizard Tournament (24 November 1994) and then returning to the Forbidden Forest during early September 2020
This event sets in motion the Roseless Timeline from Nick Moline's essay "Albus Potter and the lesson in Quantum Mechanics".
From the Web
The theatre production opened in the West End of London at the Palace Theatre on 31 July 2016, with Anthony Boyle in the role of Scorpius Malfoy and Sam Clemmett as Albus Potter: Harry Potter and the Cursed Child, Parts One and Two
Harry Potter Wikia: Triwizard Tournament