"Did you see the look on Chang’s face when Ginny got the Snitch right out from under her nose?"
-- Ron Weasley to Harry (OP31)
During the Gryffindor vs. Ravenclaw Quidditch match, from which Harry Potter is banned from playing, he and Hermione Granger go with Hagrid deep into the Forbidden Forest to meet his giant half-brother Grawp (OP30).
In spite of Slytherin supporters singing “Weasley is our King” to upset him, Ron Weasley makes some spectacular saves. Ginny Weasley’s capture of the Snitch means that Gryffindor win that year’s Quidditch Cup. The lyrics of “Weasley is our King” are changed to reflect Ron’s prowess and the team’s glorious win (OP30).
“Weasley is our King,
Weasley is our King,
He didn’t let the Quaffle in,
Weasley is our King …”
Weasley can save anything,
He never leaves a single ring,
That’s why Gryffindors all sing:
Weasley is our King.”
This takes place after Harry gets Careers Advice from Professor McGonagall (and Fred and George spectacularly leave school) in late April 1996 and after the Easter holidays (OP29). We are told the match would take place "on the last weekend of May" (OP30), which by the school calendar would be Saturday 30 May 1996. The exams begin shortly afterwards at the start of June (OP31).
From the Web
Harry Potter Wiki: Quidditch
MuggleNet podcast: Episode 15: "Quidditch-Palooza!" from the Reading-Writing-Rowling series
Dwelling on Dreams podcast: Episode 8: Snidgets, Bets, and Queerditch Marsh
The-Leaky-Cauldron essay: Quidditch in Harry Potter
WizardingWorld (Pottermore) features: