Factual error: After returning to the Dursley's after the dementor attack It is dark, this shows again when Vernon puts Dudley in the car. However, the howler from Mathila Hopkirk says that at 6:23pm Harry performed illegal magic. As the side story shows it is a hot summer, it wouldn't get dark until way past 8pm. (00:04:53 - 00:07:20)
Suggested correction: Fairly certain the film was clear that the reason it got dark was because of the dementors, they have the ability to change the weather to depressive darkness.
Continuity mistake: After the battle in the Hall of Prophecy, when Harry and the others land in the Death Chamber, Ginny is a good bit of distance away from Harry's feet in the side shot as they're all lying on the floor, but two shots later as they're starting to get up Ginny's head is now right beside Harry's knee. (01:52:25)
Continuity mistake: When Harry is narrating a letter to Padfoot, he sees a Thestral flying in the far distance, and it disappears behind a mountain. He hikes (presumably) all the way to where he thinks the Thestral went, and he finds Luna Lovegood in a clearing with a few Thestrals. For one thing, the Thestral that disappeared behind the mountain was MILES away, and it would have taken Harry a couple of hours, at least, to hike that distance through mountainous terrain. But, when he arrives at the clearing with the Thestrals, the daylight hasn't changed at all (should have been noticeably different lighting). Once he arrives there, he sees that even the largest Thestral is no bigger than a horse. But, when he first saw the Thestral disappear behind the mountain, at that distance the Thestral was about the size of a commercial jet airliner.
