Calendar

Years
A quick bit of googling tells me that a Martian solar year is about 687 terran days long, or 668 Martian days.  That's near enough to 2 terran years for me, so I'm happy to say that a 40 year old Martian is the equivalent of an 80 year-old human.  You could also infer that 8 years is the age of majority for Canal Martians (remember, octal number systems?).  It also allows me to make estimates of terms of military service.  (Yes, it actually is vaguely relevant to wargaming.)  And that little tidbit has set me to wondering what a Martian calendar might look like.

Weeks
The Martian week is 8 days long.  It is common for workers to have a 2-day rest period during a week, but there are no standardised "weekends", these depending on local custom.

Months
Months are a problem, as the Martian moons move too quickly to be measures of extended time.  However it makes sense to have an analogous grouping of weeks into something shorter than seasons.  I'll call them months, each of which is 4 weeks long. 

So far so good, but  this is where it gets a little more complicated. Sit back and bear with me as google and I get this to work.


Seasons
The axial tilt of Mars is quite similar to that of Earth (25.19° vs 23.44° if you must know), which should give it a similar seasonality. In addition the orbit of Mars is significantly more eccentric than that of Earth, and this adds to the differentiation of seasons between hemispheres. Based of perihelion, aphelion, (closest and furthest from the sun respectively) and equinoxes, the Martian year breaks down as follows:
- Northern spring, southern autumn: 193 days.  
   - 6 months long, each of 4 x 8 day weeks (192 days)  
- Northern summer, southern winter: 179 days. 
   - 6 months long as above, but with the midsummer/winter week only of 4 days (188 days)
- Northern autumn, southern spring: 143 days.  
   - 4 months long, each of 4 x 8 day weeks (128 days)
- Northern Winter, southern summer: 154 days.
   - 5 months long, each of 4 x 8 day weeks (160 days) 

The northern hemisphere tilts away from the sun when the planet is at its perihelion, and toward the sun when at aphelion. Because of this the temperatures are less extreme in summer and winter than in the southern hemisphere.  


That gives me a standard calendar system (no doubt instituted by Seldon) with very regular seasons that are a close fit to "average" seasons. 

In Space:1889 the year is split into the seasons that vary from place to place, and depend on the flow of water in the canals.  These are: 
 - Flood: a short season when meltwater rushes down and overflows the canal system, whose end marking the beginning of the growing season;
 - Flow: normal levels of water in the Canals - equivalent to Summer and Autumn on Earth; 
 - Low Flow: dry season, when no more melt is coming off the icecaps and water is at its lowest, and 
 - Surge: as might be expected tom the name, a surge of water that occurs during low flow and reflects the Flood water lapping up/down from the other hemisphere.

No doubt each city state will have local holidays and celebrations to mark the start or close of these phenomena.  

From the above I'd also guess the following:
1) Flow will be longer in the north than in the south as the heating of the icecap is spread out over a longer period.
2) Flood will be faster and higher in the southern hemisphere as the heating will be more rapid as it approaches closer to the sun when tilted towards it at perihelion.
3) Surge will be correspondingly more apparent in the North than in the South.

OK, that's enough theorising.  Back to wargames soon.