The Martian Business Calendar [1] describes a hypothetical calendar for Mars. It's only marginally more complex than the Gregorian calendar we currently use and the tradeoffs made are interesting to read about (it includes a “leap week” instead of our “leap day” and the reasons for it are both rational and irrational at the same time, depending upon your point of view). But what I would like to see is a Venusian calendar—what tradeoffs have to be made as the Venusian day is longer than the Venusian year.