"I’m out there, hearing about it. Theodore Nott - it was me who heard the rumours about the Time-Turner and me who acted upon it."
-- Harry Potter (CC1.5)
Harry turns over the Time-Turner to Hermione Granger, the Minister for Magic, for safekeeping (CC1.5).
Occurs the day before the start of term at Hogwarts, when their children Albus Potter and Rose Granger-Weasley are due to start their fourth year - so therefore takes place during 31 August 2020.
From the Web
The theatre production opened in the West End of London at the Palace Theatre on 30 July 2016, with Jamie Parker as Harry Potter and Noma Dumezweni as Hermione Granger: Harry Potter and the Cursed Child, Parts One and Two