Both of next month’s Mars Exploration Rovers will debut a new concept in telling interplanetary time. On board will be panoramic cameras and color calibration targets so the pictures beamed back to Earth will give a realistic view of what the landscape offers. On these rovers will ride an elegant and age-old method of marking the motion of our star: the sundial. Astrobiology Magazine talks with Bill Nye about how the Planetary Society is letting Earth sundials in for some of the same science to be seen on Mars.