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As I was looking into solutions for another question, I found myself wondering whether it was possible to use .NET's Calendar class to implement a calendar that wasn't based on Earthly conventions.

For instance, Mars' day is about 2.7% longer than a day here on Earth:

A convention used by spacecraft lander projects to date has been to keep track of local solar time using a 24 hour "Mars clock" on which the hours, minutes and seconds are 2.7% longer than their standard (Earth) durations.

Is there any good way to implement a MarsCalendar such that the length of a second is different from the standard GregorianCalendar, and thus be able to use DateTime objects based on it for all the standard AddDays(), AddHours(), etc. functions? (Note: Ideally, a solution - if one exists - would be applicable to any form of planetary object for which it is possible to define both "1 day" and "1 year" of consistent lengths. Mars makes for a great example, though)

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    hmmm that would be the first time I see martians dependant on our technology :P
    – user2711965
    Commented Feb 21, 2014 at 16:41
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    There should be a badge for "Best question of the day", and this should win it!
    – Sean
    Commented Feb 21, 2014 at 16:45
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    @DavidKhaykin - Once you get up to anything larger than a day, the 2.7% conversion breaks down. Hours/minutes/seconds are based on rotational speed, while Days/Months/Years are based on orbit speed. On the other hand, Calendar already supports setting arbitrary numbers of day per year.
    – Bobson
    Commented Feb 21, 2014 at 18:02
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    FYI, it's not a C# Calendar class. The same class can be used by VB.NET or any other .NET language. It's the .NET Calendar class.
    – John Saunders
    Commented Feb 22, 2014 at 2:09
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    This is kind of interesting. ANY earth-based calendar would simply be pointless in the context of tracking time on Mars. In Earth time, Mars rotates in 29 hrs, 39 minutes, 35 seconds. A Martian year is 1.8809 Earth years. But if Mars is your frame of reference, all of that is meaningless. Your day is just however long it takes for Mars to rotate about its axis one time. Divide that into a convenient number of slices, you get "hours." Divide those, you get minutes, divide those and you get seconds. The divisions are just mathematically handy, with no meaning beyond what we ascribe to them.
    – Craig Tullis
    Commented Feb 23, 2014 at 20:23

1 Answer 1

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There are several non-Gregorian calendar classes derived from System.Globalization.Calendar within the Globalization namespace (i.e. JapaneseCalendar). You should be able to implement your own. I'd whip up a sample, but there are 16 abstract methods in the Calendar class...

You might even be able to simply derive your class from GregorianCalendar and just override the GetMilliseconds(DateTime) method, returning the base's return value multiplied by 1.027d.

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    Interesting. Would that propagate up to larger time increments, or would I have to override each one separately?
    – Bobson
    Commented Feb 24, 2014 at 18:14
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    After a bit more research into the other calendars, I'd guess that GregorianCalendar and the other calendars use the Ticks property of each DateTime passed to it for the math behind all of its GetX methods. It gets complicated with DateTime values, because the DayOfYear, DayOfMonth, and DayOfWeek properties are clamped to earthly values. There are no calendars built-in to the System.Globalization namespace that have more than 12 months or more than 365 days (though some have less days), so I'm guessing those clamped values can't be overridden, so you might need your own DateTime structure.
    – Michael Hoffmann
    Commented Mar 3, 2014 at 3:54

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