I tried to include some information on the current season of Mars into my realtime simulations (Mars clocks). Now one way of doing so that I can think of (but haven't really seen it around) is to calculate Earth equivalent dates for Mars, such that summer solstices are always on the "21-Jun" etc. Naturally these "days" (based on orbit around Sun rather than rotation of Mars) last about twice as long as on Earth (more precisely: 686.9 / 365.25 times as long). Using the only solstice I know (summer solstice 25 Jun 2008 ... Phoenix was there), this approach says that it would be 23 October on Mars now. Does that make sense? Is that useful?

The general idea makes sense to me and I think it would give folks who aren't familiar with the Martian seasons and LS numbers a better gut feeling for where things are in terms of the Martian year. One small point to make is that there is a Northern Hemisphere bias in your comment - obviously although it was the summer solstice for Phoenix at the time it was also the Winter solstice for Spirit and Opportunity as both are in the SH. It has to be biased one way or the other and the Northern Hemisphere is the default but having spent a lot of time in the SH here on Earth myself I can't help but point out that not everyone automatically associates "January" with winter and July with "summer".

Also, Mars' elliptical orbit means that some seasons last much much longer than others. I have a page on the topic of Mars' calendar here. In brief, Mars' northern hemisphere spring is 194 days long; summer, 178; autumn, 142; and winter, 154. So there's some slosh of dates within the calendar. I'd take Earth calendar dates and turn them into solar longitudes, then convert from that based on Mars Ls to Mars dates.

My 2c.

--Emily

Ah never too old to learn something new I should be able to vary the length of the seasons to match Emily's website ... in due course ...

In order to compare observations from different "Mars years", one can adopt a system similar to that used in some recent
atmospheric research. A web-calculator may be found at:

http://www-mars.lmd.jussieu.fr/mars/time/martian_time.html


The zero-point of such a system is obviously somewhat arbitrary. Using the convention of Clancy et al. (2000) and
the NAIF files -- naif0008.tls, de421.bsp, pck00008.tpc -- Mars year 1 begins at 1955-04-11 10:43:58.223 (to single
precision floating point for Ls=0). I have attached a file with the MY and Ls for each day at 0h00 UTC since Jan 1, 1955. Note
that this includes a "year 0" as an artifact for the period prior to the beginning of year 1. I have been told that this
is not a valid convention, but since I hadn't envisioned referencing observations from this period, I haven't fixed my
script (yet).