Working on a SciFi story involving Martian colonies I've been stuck for an answer as to how people would handle dates. Think of how many things in your life require dates. Mortages and car loans, the deffinition of who is and who is not yet an adult, tracking the progress of a "FedEx" shipment, booking a vacation cruise, dates are important things in life. So now suppose people, lots of people, WERE living on Mars. From what I can see there just ISN'T, and probably never will be, anyway at all of using one calendar system for both Mars and Earth. Time isn't so much of an issue, at least locally. An extra 37 minutes in people's daily lives doesn't look to me to be any real issue - until - you have to translate it into GMT Earth time. But by the time people are living on Mars I doubt having a calculator around to tell you what time it is in London or Kansas City before making a call will be much of a problem. But that's all SciFi, so lets just leave that behind for the moment. In the "real world" - does Mars have its own "official" chalendar yet?