I found this interesting article about a special item included with both of NASA's Mars rovers, Spirit and Opportunity. It is a sundial, designed by notable astronomical artist Jon Lomberg.

"The 3-inch-square plate, with an upright post in its center, has a vital mission as a color patch to calibrate the rover's panoramic camera, but it will also allow children on Earth to mark Martian time."

So, it's more than just a symbolic item. Even in this technological age, sometimes the best tools for the job are those which have been around for a long, long time. Checkout the article for more interesting information.