# Does Mars have it's own calendar yet?

1. Mar 26, 2005

### MonstersFromTheId

Working on a SciFi story involving Martian colonies I've been stuck for an answer as to how people would handle dates. Think of how many things in your life require dates. Mortages and car loans, the deffinition of who is and who is not yet an adult, tracking the progress of a "FedEx" shipment, booking a vacation cruise, dates are important things in life.
So now suppose people, lots of people, WERE living on Mars. From what I can see there just ISN'T, and probably never will be, anyway at all of using one calendar system for both Mars and Earth.
Time isn't so much of an issue, at least locally. An extra 37 minutes in people's daily lives doesn't look to me to be any real issue - until - you have to translate it into GMT Earth time. But by the time people are living on Mars I doubt having a calculator around to tell you what time it is in London or Kansas City before making a call will be much of a problem.

But that's all SciFi, so lets just leave that behind for the moment.

In the "real world" - does Mars have its own "official" chalendar yet?

2. Mar 26, 2005

### misskitty

I don't think Mars has its own calender yet. Although I'm sure some one out there is working on it. It has to do with how many hours it takes to make one revolution. As well as how many times it does that and how long it takes to make one complete trip arounf the sun. Shouldn't be that difficult to calculate. So maybe it does have its own calenfer.

3. Mar 26, 2005

### hypatia

one day on mars is 24.6 hours..I'd more then likely go with the Sidereal orbit of 687 earth days to a year {about 1.88 earth days}

4. Mar 26, 2005

### misskitty

Mars is closer to the sun than we are right? So wouldn't that make their days and calender year shorter than on Earth?

5. Mar 26, 2005

### tony873004

Nasa refers to a martian day as a Sol. When you read about the Spirit or Opportunity rovers and they say stuff like sol 320, it means 320 martian days which would be more in Earth days.

That's the closest to a calandar I've ever heard. I doubt until humans colonize Mars that one will be invented that will catch on.

But, if we wanted to make our own:

Earth has 7 days named after the 7 celestial objects that move against the background stars:
Sunday: day of the Sun
Monday: day of the Moon
Tuesday: day of Mars
Wednesday: day of Mercury
Thursday: Day of Jupiter
Friday: Day of Venus
Saturday: Day of Saturn

How about a 9 day week for Mars. I always thought that a 6-day workweek and an 3-day weekend would be cool, (as well as a 25 hour day.)

Sunday : Day of Sun
Phoday: Day of Phobos
Deiday: Day of Deimis
Monday: Day of Moon (earth's moon, easily visible from Mars)
Geoday: Day of Earth
Wednesday: Day of Mercury
Thursday: Day of Jupiter
Friday: Day of Venus
Saturday: Day of Saturn

6. Mar 26, 2005

### Janus

Staff Emeritus
7. Mar 28, 2005

### Phobos

Staff Emeritus
Nope...Mars is the next planet out.
Sun -> Mercury -> Venus -> Earth -> Mars....

If it were closer in to the sun, then its year would be shorter (faster planetary orbits closer to the sun). But the length of its day would depend on its rotation on its axis, not its distance from the sun.

8. Mar 28, 2005

### TOKAMAK

Just out of curiosity, does anyone know what would be the angular width (correct term?) of Phobos when viewed from the surface of Mars?

9. Mar 28, 2005

### chroot

Staff Emeritus
http://en.wikipedia.org/wiki/Phobos_(moon)

- Warren

10. Mar 29, 2005

### Grogs

I worked on this a bit for the same reason (Sci Fi type book.) The system I came up with was 1 martian day = 1 sol (24.6 hours => we really luck out with this being so close.) 1 martian yr = 669.6 sols. I divided this up into 12 periods. 9 of them are 56 sols long (8x7), 2 are 55 sols long, and 1 is 55/56 sols long for the leap year that would occur 6 out of every 10 years.

As far as conversion, I don't think it would be done directly, except by computers. Every clock/wristwatch/etc. would need to display 2 different times, local time and 'Universal' time. On planets with a fairly earth-like period of rotation, like Mars, people would live and work on local time and use universal time when dealing with people from other planets. On a planet like Mercury with it's 88 day long 'days', everyone would probably just work off of universal time and local time would only be of interest for determining when you were on the sunny or dark side of the planet.

11. Mar 29, 2005

### ohwilleke

Hours, Dess, Centits and Mills

I would suspect that the Martians would find it useful to adjust their daily clock. I think they would find a 24 hour day convenient (because it allows the adaption of traditional clock designs, eight hours shifts, noon and midnight language, etc.). This means that the Martians need to fit 98.9 extra seconds into every hour. One way to do this would be to have a 1.02747 second long Martian second, but that would mess up SI units. A easier approach might be to use decihours (the favorite unit of time for lawyers and accountants) and centihours (rather than minutes) and millihours (rather than seconds), in customary local time measurement. Thus, a decihour would be 6 minutes and 9.89 seconds long, a centihour would be roughly 37 seconds long, and a millihour would be roughly 3.7 seconds long. This might be abbreviated to a "dess" (not conjugated to distinguish between the singular and plural, e.g. "one dess", "three dess", "a few dess"), a "centit" (in lieu of a minute) and a "mill" in popular conversation. A Martian Hour might simply be called an "hour" with an Earth hour called a "Standard Hour". The term "second" would always refer to the SI unit.

The time of day would be reported as, for example, "six point five eight o'clock". As in military time, there would be no AM and PM, only twenty four numbered hours. Thus, "fourteen point two one o'clock".

Sols and Weeks

I would expect that the people of Mars would adopt the natural Martian synodic day (midday to midday) (the 24 hour, 39 minute 35 second Sol), as people have been shown in sleep research to gravitate towards a little longer than 24 hour day when stripped of external references anyway, and would also probably adopt a seven day week, as it is familiar and has no connection to astronomical phenomena in any case. I suspect that the names of the days of the week would stay the same.

Months and Years

I would also think that a roughly menstrual based four week month (28.7 Earth days) called "months" with 24 months in a Martian year (in symmetry with the hours of the day, double the number of Earth months and each quite comparable in length to an Earth month), would be a useful figure (for things like accounting and billing purposes). Of course, this gives 672 sols in a year, rather than 669.65972 synodic days, so you would need two 27 sol months every year, and and another 27 sol month (a "skip day") in years divisible by three which would be called skip years (with an additional adjusting skip day every 144 years). One plausible way to space the short months would be to have the annual short months on the 8th and 16th months, with the skip month as the 24th month in a skip year. Every 144 years (a "grossery"), there would be an extra skip year, unless it fell on a skip year, in which case the extra skip year would be the following year. This would be one day off the true year every 3,126 years.

The symbolic time to start counting years would be the year the first human arrived on Mars. Years after the year zero of arrival would be AA (for after arrival). Years before this point in time would be BA (for before arrival). The symbolic month to start the year would be the first month of Spring at the equinox.

Choosing names for the 24 months of the year would be quite political. Since Mars has seasons, breaking them up into quarters of six for summer, autumn, winter and spring would make sense. To avoid confusion with Earth dates, names from other calanders might be used, for example the Hebrew, Chinese, Islamic and French Revolutionary calanders. An idea I like in particular is that a city name could be chosen from twenty-four sections of the Earth to name each month. For example, the months might be:

Summer: Paris (Par.), Cairo (Cai.), Moscow (Mos.), Tehran (Teh.), Mumbai (Mum.), and Kathmandu (Kat.).
Autumn: Bangkok (Ban.), Shanghai (Sha.), Tokoyo (Tok.), Brisbane (Bri.), Tarawa (Tar.), and Auckland (Auc.).
Winter: Nome (Nome), Oahu (Oahu), Juneau (Jun.), Seattle (Sea.), Denver (Den.), and Mexico (Mex.).
Spring: Boston (Bos.), Caracas (Car.), Rio (Rio), Canary (Can.), Dakar (Dak.), and London (Lon.).

Note that annual skip months would be months starting with "S".

Dates would be written in the European convention. For example, 5 Seattle 36 AA would be the fifth day of the month of Seattle in the year 36 after arrival. Of course, AA would usually be left unstated, while BA would normally be noted expressly. Also, months would usually be abbreviated. Thus, 25 Lon. 45 would be a more typical written date.

Holidays and Special Days

Arrival Day would probably be a major holiday, as would be New Year's Day, and indeed, probably the first day of each season.

As far as significant ages, ten Martian years old would be a convenient time for adulthood. This works out to be eighteen years and just under ten months in the Earth calander. Age thirty-five in Martian years (65.8 years) might be a marker for senior citizen status. Children would probably celebrate half-birthdays as well as birthdays. Adults would probably enjoy having birthdays half as often.

Legislative elections would probably be held once per Martian year, perhaps in the month of London with newly elected officials to take office the following month of Paris, as modern technology would permit fairly rapid vote counting.

Schools might be on-half quarters (three months each) called semesters (instead of conventional semesters), and might have a four day weekend semester, and a three week break at the end of each semester. Kids get bored in a full three month summer vacation which doesn't make sense in a modern economy anyway, but do need occassional lengthy breaks. The aggregate time off would be similar to the current system with its summer vacation, Spring Break, Christmas vacation and numerous holidays.

I would suspect that there would be a split between Orthodox religious people, who would keep track of Earth days for celebration of religious events (with the ultra-orthodox keeping even the Earth Sabbath) and ordinary religious people who would adapt most of their holidays (with the possible exception perhaps one holiday, like Easter, for Christians) to fit the local calendar.

Use

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Last edited: Mar 29, 2005
12. Mar 29, 2005

### MonstersFromTheId

Grogs & Janus

Gotta say I loved Janus' post on "bring a calendar" ;-).
But, like Grogs, I'm thinking more in terms of people having to deal with differing calendars on different worlds, and in the end, I just can't believe that people will actually use different calendars.

For one thing conversions would get just too dammed confusing and frankly cost too much. This whole issue could get to be a MUCH knottier problem than "U.S. units vs. metric", and require much more thinking and converting than people are going to put up with in their daily lives.

For another, even living on a world like Mars, let alone a deep sea colony on Europa, is undoubtedly going to be very much an indoors affair. "Seasons" aren't all that relevant to non-agrarian cultures like those of ;-) "modern" industrial societies" as it is. And imo they're likely to be considerably less relevant on extra-terrestrial colonies.

Take Europa for example. Deep sea colonies on Europa are unlikely to give the slightest damn whether or not it's night or day on the surface of that world. I really doubt that they'd even bother with time zones. Under 90 some miles of ice, and one HECK of a lot of water, it seems to me that the only thing likely to differentiate "night" from "day" is when the lights go on and off. When "night" and "day" begin or end becomes basically a choice, and the simplest choice I can see is to just have ALL of Europa work on Earth GMT time.

Ditto for places like Mercury or even Venus. Leaving a colony to go "outside" on a world like Mercury or Venus would likely be about as dangerous and rare a thing for people to do as visiting the bottom of the ocean is now on Earth. It would be done, but not by your "average Joe", and the kids certainly wouldn't be along for the ride.
Over time, with colonies in exceptionally harsh environments, I'd expect that the interior of the colony would eventually be a very nice place to live, a nice place to raise kids, but it'd be a bit like living in any major metropolitan area. "Hiking" is something you do on vacation someplace else.

And ditto for "orbitals", large colonies in the L-4 / L-5 Lagrange points or in "The Belt" (colonies on asteroids).

Bottom line: colonies in exceptionally harsh environments wouldn't really need their own calendars, or even time zones. They'd just use Earth GMT because "it's what everyone else uses", and it's convenient.

But colonies in marginal environments, like colonies on Mars, might be different. "Outdoors" might be off limits for young children, but perhaps not for adults and adolescents. People may in fact "go hiking", they might even fly kites, or attend large outdoor events like air shows.
The bottom line with places like this is that, if "the average Joe" sees the sky and leaves the interior of a colony often enough, then having "day" correspond to when the sun is up is probably enough to warrant using a local time reference in people's daily lives.

So for Mars I've come up with something pretty close to what Grog is thinking.
For example -

Mars hours, minutes, and seconds = Earth hours, minutes, and seconds.

A Mars "day" = 24 hours and 37 min with the extra 37 minutes referred to as "Drop Time", a period of time inserted just before noon, and traditionally used as a lunch break. At "noon" Martian clocks and wristwatches essentially stop, count down the 37 minutes, and then continue on just like an Earth clock or wristwatch.

A Martian week consists of 7 Martian days, each with the same name, and with Sat and Sun still constituting "the weekend".

But there are no Martian months or Martian years.
Or more accurately they're not widely used. For periods of more than a week, and all official records, Earth GMT is what I'd expect to be used as a universal time reference on any Earth colonies. Birth records, the dates on legal documents, calculating interest on loans, etc, would, I expect, all be done based on Earth GMT time references, even on Mars.
Even birthdays would likely be celebrated based on an Earth year having passed so that people don't have to convert ages as in "dog years" "Earth years" and "Mars years".

Basically I think it will come down to need and convenience much more than things like the phase of a local moon or moons, or local a local summer solstice. Colonies on other worlds are unlikely to resemble agrarian cultures where the growth cycle of crops is central enough to life to warrant basing a calendar on it.

13. Mar 29, 2005

### ohwilleke

I agree that people who didn't see the Sun or had a completely radically different from Earth situation (like months long days) would probably use Earth GMT. But, in a place like Mars, I think local calendars would be used primarily. Using Earth time would screw up your sleep cycle (indeed it was a real hassle for Earth crews trying to staff the Mars probes), and I think that Martian colonies would, at least, have windows and natural sunlight, even if people didn't go outside. Also, on Mars, the impact the seasons would have on the polar caps which would be key to daily survival, and on the length of the day, would make seasons somewhat relevant. Indeed, sunlight through windows, rather than any actually outdoor experiences, is probably what would make local time so attractive to Martians.

Even places like Hawaii get very out of touch with the time rhythms of the continental United States. This would be even more true on Mars. Interplanetary trips would likely be confined to a small elite, as they would be far more expensive than on planet trips, and those who had regular dealings with Earth would probably just have an Earth clock on display in their office or on a watch -- this is what multinational business offices and airports often do now -- have a clock displaying the time in every place you might want to do business. Moreover, travellers from Mars could adapt away from local time during their long trip to somewhere else.

Using Earth hours on Mars with its drop time, would probably turn out to be quite inconvenient for purposes like scheduling people to work shifts and calibrating local environmental equipment and setting alarm clocks. Conversion would be a pain, but if most legal documents, loans, etc. were with local businesses (which you would expect on Mars), local time makes more sense than other time schedules to do the calculations.

Also, cultural differences in birthdays and the like wouldn't be unusual. And, permanent Martian settlers would likely have a strong desire to develop their own regional identity. For example, in Korea it was customary to state your age as one year older than it is, to include the pregnacy period. Japan has holidays not celebrated in the West, causing its stock market to be closed at times when European markets are open. Interplanetary transactions would probably be conducted in Earth GMT, but I suspect that those would be confined to big business. In the same way, lots of international monetary transactions are conducted in Internatioal Drawing Units, but few people know what one of those are worth.

Of course, SI units would be used on other planets for all matters other than daily time keeping. I imagine that on many planets, however, Kelvin would prove to be a more commonly used scale for external temperatures than degrees C.

Note also that Mars would probably have time zones, similar to those on Earth and probably not mathematically regular, to keep populations that interact with each other often in the same time zone.

Last edited: Mar 29, 2005
14. Mar 29, 2005

### hypatia

I'd imagine he looks very tiny :rofl:

15. Apr 1, 2005

### Nereid

Staff Emeritus
But not smaller than Nereid, right?!?

16. Apr 1, 2005

### misskitty

I stand gracefully corrected. Thank you Phobos.

17. Apr 2, 2005

### countryboy

What would the time dialation on Mars amount to? I have heard that on other planets where the gravity is more or less, that time either slows or quickens accordingly.

18. Apr 2, 2005

### ohwilleke

The difference in time dialation would be negligable. I haven't actually done the calculation for Mars, but I have looked at the calculations for Earth, and they would be on the same order of magnitude which is so slight as to be incapable of being noticed without very precise instrumentation.