Continuity mistake: Odysseus' hair constantly changes throughout the scene where he is talking to Athena on his ship.
Continuity mistake: Aeolus changes position on his chair between shots of him saying "Everyone knows Odysseus, the great hero who built the Trojan horse".
Continuity mistake: In the scene where Odysseus is climbing up the hill and sees the god Hermes, Hermes plucks a plant to feed Odysseus. Odysseus' head rotates to the left between shots.
Continuity mistake: Telemachus drives Antinous to the wall with a spear and stakes him to the wall. The spear is actually gone when Odysseus looks around the room after killing everyone.
Continuity mistake: When Antinoos throws the bow to the ground after failing to string it, it lands tilting upwards. But by the time Odysseus picks it up, the bow is lying flat on the ground.
Continuity mistake: Throughout the battle in the throne room at the end, the position of many of the dead suitors changes between shots.
Continuity mistake: During the Trojan war, when Odysseus and Achilles get surrounded by Trojan soldiers, the position of the soldiers change between shots.
Continuity mistake: When Penelope is making olive oil she pours a basket of olives into another empty basket. Between shots, the basket with olives moves closer to the empty basket.
Continuity mistake: When Odysseus is telling Calypso about his scar, he rises from the water. In one shot his head is down and his arm is lowered. In the next, his head is up and his arm is raised.
Continuity mistake: The blood on the face of the little boy at Troy changes constantly throughout the many shots of him.
Continuity mistake: When the Trojan Horse was being inspected by King Priam and his men for the first time, why didn't he see the Greek soldiers hiding inside? There were plenty of large gaps between the planks used to construct the horse.
Answer: The Trojan War itself was a decade long, followed by Odysseus' ten-year journey home to Ithaca, so all told he was gone roughly twenty years.