Continuity mistake: In the scene where everybody's singing about Gaston, the legs of the chair he's sitting on change between shots.
Continuity mistake: When Maurice looks up at the castle after he has just arrived, a lion's head is carved over the front door. But when Gaston leads the villagers to the castle later in the film, the lion's head has been replaced by a green shield.
Continuity mistake: When Lumiere suggests to see "The gardens or the library" his flames are at his sides. Then when Belle replies "You have a library" his candles are at his sides.
Continuity mistake: The cracks on the mirror seen while the Beast is taking a bath change between shots.
Continuity mistake: After Belle refuses to go to dinner with the beast, he bursts into the West Wing and we can see the hallway outside the doors. It's completely different than when Belle comes down it later.
Continuity mistake: When Belle sits down on a fountain to read the blue book she got from the librarian, some sheep pass by and one of them bites a piece of the page off. But in the next shot, when Belle sings "But she won't discover that it's him til chapter three.", the page is intact again.
Continuity mistake: After the wolves run away the Beast is shown standing in the snow before collapsing and there are five cuts on his arm. However, when Belle treats the wounds in the next scene, there are only three cuts on his arm.
Continuity mistake: In the 'Human Again' song, near the end of the song Cogsworth and Lumiere turn on the fountain and the large middle statue sprays out water, but the two statues either side of the middle one are turned off. Then the wardrobe jumps out onto the balcony singing and then it cuts to an ariel shot, and now the two side statues are suddenly spraying water too. (00:58:45)
Continuity mistake: In the overhead wideshot right before Maurice walks in there's a green mat by the doorway, and nothing hanging over the large window, but when Maurice walks into the tavern there's a blunderbuss hanging over the large window, and the mat has vanished.
Continuity mistake: After Maurice is thrown out of the tavern Gaston whispers his plan to LeFou, and when they begin to dance we see an angled wall with a dart board, bow and arrows, but the problem is that angled wall with the dart board, bow and arrows did not exist in the overhead shot, right before Maurice walked in.
Continuity mistake: During Gaston's song, when they sing "Give five hurrahs, give twelve hip-hips," LeFou's beer tankard switches from his left hand to his right hand, between shots. Additionally, one of the wall's wood beams near the fireplace has vanished behind LeFou, then reappears. The same thing happens again later, after they toss Maurice out the door.
Continuity mistake: During scenes at the tavern, the shelves between the brew barrels keep changing between being quite ornate to being ordinary shelves.
Continuity mistake: While Beast is bathing in the bathtub Lumière is standing on a stool with two level foot rest bars, but in the following shot the stool has only one level of foot rest bars, then it's back to two levels again.
Continuity mistake: After being stabbed with the arrow, Beast falls over a balcony and then falls over on another rounded balcony, next to the edge. Then the angle changes and Beast is lying on the middle of a long rectangular structure.
Continuity mistake: When the Beast shows Belle to her room and then says she will join him for dinner before shutting the door, Belle is wearing her cloak. She's still wearing it when she runs over to the bed, kneels down and starts crying. When we see her again (after the Gaston scene which is in-between), she's no longer wearing the cloak, and she couldn't have removed it at any point because her position next to the bed hasn't changed since she started crying and she doesn't move again until Mrs Potts taps on the door to offer her a cup of tea.
Continuity mistake: When Belle comes down to dinner she leaves her coat in her room. Later, after Belle runs out of the West Wing, she grabs her coat while running down the stairs.
Continuity mistake: When Belle goes to open the door for Gaston, her chair is close to the carpet on the floor. Then when the shot returns to this area, the chair is much further from the carpet.
Continuity mistake: When the Beast shows Belle to her room, in a wideshot you can see the oval centrepiece of the foot of the bed has a large purple rose painted on it and it has a plain red border. In a later scene after Mrs. Potts and Chip leave Belle's room, the purple rose and red border have vanished from the centrepiece, which is now only decorated with evenly spaced gold dots. (00:24:35 - 00:31:05)
Continuity mistake: When Gaston is telling Belle all she has to do is marry him, and her father will be let go from the asylum, his hands are bare. Then when Belle gets the magic mirror and cries "Show me the Beast!", Gaston has yellow gloves on. Then in the next shot they're gone again. (01:07:25)
Continuity mistake: When Belle and the Beast go and sit outside after the ballroom scene, when the Beast asks Belle "Are you happy here with me," between shots Belle's hair goes from being normally hanging down by her back, to resting over her right shoulder. (01:02:45)
Answer: In the prologue, it states that the Beast must find true love by his 21st birthday, and that he had been cursed for ten years, so since his relationship with Belle takes place as the deadline approaches, he must have been 10 when he was cursed.