The sun is rising.
To James Cameron’s credit, he did his utmost to make sure the ship’s voyage was as realistic as possible. However, because we know the Titanic’s true course, we can discern when he was mistaken. Jack and Rose are spitting over the deck during sundown, right before supper, in the famous deck-spitting scene. Because they’re on the ship’s port side, it’s sailing north-west, despite the fact that it’s actually travelling south-west. We understand that it’s a minor annoyance, but it’s still a mistake.