Martian calendar and timekeeping Options

[Hal Fulton]

Hello, all...

As a space enthusiast (especially Mars) and as a Ruby programmer, I have
taken an interest in Martian calendars and clocks.

Here (attached) is an article I wrote (basically for a non-technical audience)
on "my" Martian calendar, the Martian Common Era calendar.

I am perhaps 95% finished with a Ruby library called MarsDate that will handle
Martian dates and times (and interconvert with Earthly dates/times).

Comments are welcome on this article.

And if anyone out there is a Ruby programmer, or even a programmer in general,
I'd love to have some opinions or even assistance on this library.

Thanks!

Hal Fulton

Attached File(s)

 marscal.html ( 23.79K ) Number of downloads: 2072

 

[craigmcg]

Fun read! Thanks for posting.

[Phil Stooke]

Stretched seconds? Would velocities be given as meters/stretched second?

There are , as you say, lots of ideas about Mars calendars, and I welcome all ideas like this as the discussions can be interesting and imaginative. But there is a Mars calendar in widespread use in scientific circles, originated by Clancy, which will be hard to replace at this stage. In fact I use it explicitly throughout my Mars book (due out at the end of this month). In my view, changing the values of important constants like the second is a fatal flaw which would never fly in serious applications - that works well as a thought exercise but not in practice.

Phil

[Hal Fulton]

Stretched seconds would never be used for scientific measurement, of course.

I use them only because NASA does, in its official timekeeping.

Tell me more about this Clancy calendar. I thought the Darian was by far the
most famous and widespread.

Hal

[ngunn]

Link to earlier thread here: http://www.unmannedspaceflight.com/index.php?showtopic=7312

[Deimos]

So far, I have found most Martian calendar talk amusing. The Clancy calendar is practical--it doesn't need things like months, and doesn't add them. It is good at what it does, and therefore is used by those who professionally need reference to a Martian calendar. When people go adding weeks and months, I haven't seen someone try and think like someone who must use such a calendar. Picking 12 or 24 (or other) months for your calendar, based on personal preference, seems arbitrary.

Live on Mars. Or at least Mars time. Or live Earth time and operate something on Mars. The 3 most important cycles in Mars operations are 24 hours and 39 minutes, 36 sols, and 668 and change sols. In roughly that order, for operations.

The 3 cycles will be the same for people on Mars working with people on Earth as it is for robots on Mars working with people on Earth. As long as there is something on Mars that is tied to local solar time there, and is also tied to some local time on Earth, a month-like time-frame is 36 sols. The number of such months in a year is not an integer. Oh well.

36 sols is 37 days--moons that have no tidal or agricultural significance will not change that, nor will preferences for round numbers. And it will be a while before desire to express Martian birthdays drives any big change in this. People who have that problem won't care what arbitrary cycles we impose; maybe they'll go with 18 months/year and let the astronomical vs. calendar cycles drift (as some familiar Earth calendars have done with lunar cycles vs. months). But if you do not recognize key cycles, you cannot make a useful calendar.

[Hal Fulton]

Oh, so the Clancy calendar is just the solar longitude?

Practical, but (to me) boring. We could do the same on Earth, of course, or
could similarly use Earth's L-sub-s or even the so-called Julian day. But
do you really want to remember your birthday as 117, celebrate 165 rather
than July 4, and so on?

Maybe we should number our children instead of giving them names...

All kidding aside, the Clancy calendar is obviously adequate, well-known,
and useful.

Anything else is is purely for human interest, for imagination, and for fun.

I have no idea what long-term solution will be used when humans live on
Mars. I don't doubt that Ls will be used at the start. But I hope that eventually
something more interesting and more imaginative will arise.

Hal

[Deimos]

Anything else is is purely for human interest, for imagination, and for fun.

And art.

Something is either practical, artful, or amusing. (For generality, one could add some negative terms, but they are unnecessary here.) A sculptor who works with the grain to make the raw material more than it ever was--that one is an artist. One who imposes will on a subject without regard to the subject's tendencies--not so much. A Martian calendar with more detail than Clancy's seems not practical now, which is not necessarily bad. A calendar that ignores the natural cycles, the likes of which have always defined what it means to be a calendar, is inartful. I would think one would strive for practical, artful, or both, even in fun--elsewise there is little point. An artful calendar-maker does not make up cycles: find cycles, and make them into something more than they were. Or be content with an adjective other than practical or artful.

[mwolff]

Oh, so the Clancy calendar is just the solar longitude?

If you mean by solar longitude that which is called L_S (or planetocentric longitude of the sun as seen from a specific body), then not exactly...but close. It is defined by orbital position and given Mars' non-trivially non-circular orbit, L_S is (slightly) non-linear in time. In other words, if you calculate the fractional part of Mars Year by L_S/360., this will not be exactly correct.

[Hal Fulton]

@mwolff, thanks for the clarification.

@Deimos - it's true I divided the Martian year into months and weeks as well as sols.
I find this to be aesthetically pleasing for historical and cultural reasons. They are
certainly unnecessary, and it's reasonable to argue they are inappropriate. But I
like them.

However, I did adhere strictly as I knew how to the year and sol cycles. Is there
some other cycle I should be thinking of? The orbital periods of Phobos and Deimos,
I think we agree, are of minimal value in a calendar context.

Hal

[Phil Stooke]

That's a problem with Mars - there are really no other cycles to build into the calendar. I would say that means the field is wide open for suggestions, rather than closed. But it also means people may not take those suggestions very seriously.

As an aside, the first thing any Mars calendar needs to become widely used is a website with a calendar converter. This is the one I use all the time, based on Clancy's calendar:

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

With that, people can figure out what sol it is on any given day, past or future. Note that this link DOES include a month designation, but I have never seen anyone use it, and I certainly don't myself.

Phil

[Hal Fulton]

I don't expect or want to be taken *too* seriously.

I certainly don't expect my calendar to be used by future Martian settlers --
though I wouldn't object, of course.

I would *like* to think that whatever calendar those hypothetical settlers
use is not just hyper-pragmatic, but will have a very human flavor, with its
own culture and tradition. I want to see Martian holidays, if I should live so
long, and I don't want them to be called things like 294 and 356.

But all that is far beyond my control.

What *is* within my control is: Is my math correct? Does my code work?

And, as I said before, I think my code is "95% correct, with some glitches."

The point about a web site is well-taken, and I shall certainly create one
when my algorithm is a little more mature.

So again -- anyone who wants to look at this is welcome to contact me offline
(or in this forum). My email is rubyhacker@gmail.com

If you can read Javascript, you can read Ruby (it's rather like Python or
cleaned-up Perl). And anyhow, I can outline the basics of the algorithm
in pseudocode or whatever.

Cheers,
Hal

[jmknapp]

I recall a guy very actively discussing Mars calendars online around the time of Pathfinder. Just looked it up--his name is Thomas Gangale & he made a virtual encyclopedia of Mars calendar systems:

http://pweb.jps.net/~gangale4/chronium/chronfrm.htm

Lots of variations there as mental exercises, but calendars people actually use stem from mostly practical considerations and aren't necessarily based on abstract first principles like astronomical cycles. From a human perspective the solar day and the solar year seem indispensible, but what else? It could get esoteric. For example, with the current technology for getting stuff to Mars, the Earth-Mars opposition cycle of 780 days would be extremely important to any Mars residents--i.e., the Wells Fargo wagon would come every 780 days (760 sols). So, for each Mars year of 669 sols, that date would slip by 91 sols.