One year for any planet is measured by how long it takes to orbit once around the sun. Since Mars is farther away from the sun than Earth, it takes almost twice as long: Earth orbits in 365 days. Mars orbits in 687 Earth days. This Mars in a Minute animation from NASA Jet Propulsion Laboratory explains this, as well as what that means for any Mars-bound spacecraft.
Fun fact: Martian New Year begins on the planet’s Northern Hemisphere Spring Equinox. That occurred on May 5, 2017. The next two New Year celebrations on Mars will occur on March 23, 2019 and February 7, 2021.Next, watch To Mars and Back In 150 Seconds and learn more about Mars. Bonus: How does Leap Year work?