Skip to now, and Mars. NASA has these little robots named Spirit and Opportunity wandering around, exploring the planetary surface. Their programming records time in Martian days, called "sols" (short for "solar periods," I suppose), and since the robots weren't expected to last very long, the programmes were written with three-digit dates.
But for [Bruce] Banerdt [at JPL] and about 50 other scientists working on the project, what is just as amazing as what may come out of Victoria Crater is the fact that Opportunity, and its sister rover Spirit, are still going strong nearly 1,000 days into their field work on Mars.
The longevity of the little robots is beyond the wildest dreams of some working on the project.
"We would have been happy with 30, maybe 90 days," said Ray Arvidson, deputy principal investigator for Spirit and Opportunity. Arvidson is based at Washington University in St. Louis, Missouri.
So the latest software updates sent to the rovers had to include a revised date format, with four-digit dates.
Read more about it in this CNN news article, which was the source of the above quote.