What day is it on Mars?

There are many schemes to produce a viable calendar for Mars, perhaps the best known of which is the Darian calendar, which I’m working on my own alternative to.

The alternative starts with the biggest problem I have with the Darian calendar, its week cycle.  It assumes that people who live on Mars are going to want their own names for days of the week, and want every month to start with the same day.

I think that’s preposterous.

I believe most humans are comfortable with the names they already have for seven days in a week.  Since the abolishment of the French Republican calendar, the French have been keen to have a Vendredi following every Jeudi.  For us English speakers, there is a certain expectation we have going to bed on Saturday that tomorrow will be Sunday.


The key thing is… How do you decide which days on Mars are Monday or Tuesday?  I feel the best solution is to pick a particular date that the day of the week was the same on Earth and Mars … preferably a great moment in Martian exploration.

I can think of a few possible dates that might be suitable:

Tuesday, 1 Jan 1608, start of Year Zero for the  Darian calendar;
Thursday, 1 Jan 1609, start of Year One for the  Darian calendar;
Wednesday, 14 Jul 1965, the day Mariner 4, the first human space probe to Mars, flew by;
Saturday, 27 Nov 1971, the day that Mars 2 crashed onto the surface of Mars, its first direct interaction with humans;
Thursday, 02 Dec 1971, the day that Mars 3 successfully landed on Mars, the first successful probe landing.

For me, I think that the Mars 2 crash is the best day.  It’s the first time that anything manmade interacted with Mars.

There is a concept similar to Julian Date used by the Mars24 software from GISS  (whose site is unfortunately down at the moment):  The Mars Solar Date.  With some calculation [MSD = (seconds since January 6, 2000 00:00:00 UTC)/88775.244 + 44795.9998] it can be found that Sat 27 Nov 1971 1200 GMT is equivalent to MSD 34804.187.

The Martian day at the Mars 2 site was roughly 1000 GMT to 2300 GMT on 27 Nov 1971.   With MSD 34804 defined as a Saturday, other days may be determined with modulo 7.

34804 % 7 = 0 , indicating Saturday.  So, accepting my premise that the Mars 2 crash should be the day-of-week epoch, then MSDs with modulo 0 are Saturday, 1 indicates Sunday, 2 is Monday, and so on.

So Today? If my numbers are right and the MSD at 2200Z 14 Jan 2013 is 49426, then it’s Friday on Mars!

Update: GISS is back up!  You can download Mars24 here.  You’ll need Java 1.6+ to run it.

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  1. Pingback: The Martian Seasonal Calendar | j5mc design

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