If there was another planet revolving around the Sun, but further from the Sun than Earth is, its year would be longer. But its day could be anything, as it depends how fast the planet spins around on its axis, and that is not something that is not affected by the duration of the year.
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So far, astronomers have already found over 500 hundred new planets farther away from the sun. These are not planets within our solar system but instead orbit about other stars hundreds of light years away. There's no way at this time that we can determine the length of their days, but in most cases we can determine the length of their years simply by knowing their masses and the masses of the stars they circle.
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The Sun is a Star so another planet would revolve around another far far far away star.