The planet Mars takes 687 Earth days to orbit the Sun. This means that a martian year lasts 22.9 months, or almost two full Earth years. A martian day is only very slightly longer than an Earth day, so that Mars’ year is 670 martian days long. Mars’s year is longer than Earth’s because it is further from the Sun than Earth is, so that it feels the Sun’s gravity more weakly than the Earth does. This means that it doesn’t have to move as fast to maintain its orbit, and that combined with the fact that its orbital path is so much longer than Earths, leads to it having such a long year.