"You know what we've got to do. If we lose this match, we're out of the running. Just - just fly like you did in practice yesterday, and we'll be OK!"
-- Oliver Wood to the Gryffindor Quidditch Team (PA13)
Gryffindor vs. Ravenclaw in Harry Potter’s third year is the first Quidditch match where he is allowed to fly on his new Firebolt broom, which was given back to him only in time for one practice session with the team (PA13). It is a “must win” situation for the Gryffindors. They are behind in the standings since Harry’s Nimbus 2000 broom was destroyed by the Whomping Willow (PA9).
During the match, some dark figures appear below – it looks like Dementors have come onto the pitch. Harry sends his Patronus towards them while continuing to chase and then catch the Snitch. Gryffindor therefore wins the match by a large margin against Ravenclaw. It turns out, however, that these are fake Dementors – Draco Malfoy, Marcus Flint, Vincent Crabbe and Gregory Goyle disguised in black robes (PA13).
Harry is still asking Professor McGonagall for the status of his Firebolt at the beginning of February (PA12), so this match is likely to have taken place at the end of February or beginning of March.