Professor Snape referees a Quidditch match

Severus Snape is the surprise referee for this late afternoon match between Gryffindor and Hufflepuff in February 1992 (PS13).

According to Professor Quirrell, this is in order to protect Harry Potter (PS17), although of course the Gryffindors assume that he’s there to cheat in favour of Slytherin House. Harry catches the Snitch just a few minutes into the match to seal a win (PS13).

Timeline Notes

The match starts later in the afternoon, around 4 pm, which is a change from the normal 11 am start time. If Harry hadn't managed to catch the Snitch in record time, they would have been playing the dark. In fact, Harry leaves the stadium right at sunset, around 5:30 pm.

The start time for the match is derived from this passage (emphases mine):

Harry left the locker room alone some time later, to take his Nimbus Two Thousand back to the broomshed. He couldn't ever remember feeling happier. He'd really done something to be proud of now -- no one could say he was just a famous name any more. The evening air had never smelled so sweet. He walked over the damp grass, reliving the last hour in his head, which was a happy blur: Gryffindors running to lift him onto their shoulders; Ron and Hermione in the distance, jumping up and down, Ron cheering through a heavy nosebleed.

Harry had reached the shed. He leaned against the wooden door and looked up at Hogwarts, with its windows glowing red in the setting sun. Gryffindor in the lead. He'd done it, he'd shown Snape....

And speaking of Snape...

A hooded figure came swiftly down the front steps of the castle. Clearly not wanting to be seen, it walked as fast as possible toward the forbidden forest. Harry's victory faded from his mind as he watched. He recognized the figure's prowling walk. Snape, sneaking into the forest while everyone else was at dinner -- what was going on?

Sunset in mid-February in Scotland is around 5:30, so Harry would have been thinking over the "past hour" around that time. That puts the end of the match around 4:30, and the fast catch of the Snitch then puts the start of the match at 4 pm. This is the only time a Hogwarts Quidditch match starts at any time other than 11 am.

In the books, this match usually takes place towards the end of February. The fourth Saturday in February is the 22nd.