"Rose Granger-Weasley! Your daughter! ....you and Ron aren't married...."
-- Albus Potter (CC2.11)
Coming back to classes after his time in the hospital wing, Albus Potter discovers that Hermione Granger is teaching Defence Against the Dark Arts. She is outraged at his reaction to this and his questioning of her – asking about her husband and child. The other Gryffindor students accuse him of hating Gryffindor and trying to lose them points (CC2.11).
After the previous event, early September 2020 and likely the next day.
This event takes place during the Roseless timeline, as described in the essay "Albus Potter and the lesson in Quantum Mechanics" by Nick Moline.
Another shock for Albus Potter - not only is his Uncle Ron Weasley married to Padma Patil, but his Aunt Hermione is not married (and therefore his cousin Rose doesn't exist). Hermione seems embittered and agrees with Albus that she is "mean" (CC2.11).
From the Web
Pottermore: Harry Potter and the Cursed Child
The theatre production opened in the West End of London at the Palace Theatre on 30 July 2016, with Noma Dumezweni in the role of Hermione Granger, Sam Clemmett as Albus Potter, Claudia Grant as Polly Chapman and James Le Lacheur as Yann Fredericks: Harry Potter and the Cursed Child, Parts One and Two