Answer: "People will say the length of a day is determined by just the rotation rate of a planet, but that isn’t entirely true. The orbit around its sun also factors in. What we define as a day is the time between when the Sun is highest in the sky until the next time the Sun is at the highest point in the sky. This isn’t just the time it takes the Earth to rotate once on its axis, though. This is because, as the Earth is rotating, it’s also moving relative to the Sun"
