This document is part of the Martian Time Boneyard. It was originally located at
Author: Peter Kokh

Pete's Mars Pages HOME
Re: Dr. Zubrin's
Mars Calendar
Ambitious Project Ideas
M.A.R.S. on Devon Island
Technologies Needed
Role of the Moon (IMHO)
Selected Mars Articles
Moon Miners' Manifesto
A Selection of Mars Links
& Other Mars Pages
Constructive Discuss
List on Project Ideas
Seeds of Martian Culture
One Way to Mars
Meeting Mars Halfway

We can support Robert Zubrin's Mars Calendar
with the
"Friendly Amendments" Proposed Below

Recommended Reading:
Mars Calendar - Zubrin
History of Mars Calendars
Mars Time Web Site
Marstime Virtual Conference at

Richard Weidner's Mars Seasons Calendar

My "Mars Pulse" Calendar
Effect of Mars Time & Calendar on Culture

The Clock:

Zubrin proposes a 24:60:60 clock precisely analogous to the one we use on Earth with hours, minutes, and seconds all slightly longer than terrestrial values by a ratio of 1.0275:1

  • the disadvantage of this is that all science textbooks for Martian pioneer students will have to be rewritten as the quoted reaction times and values in Terrestrial textbooks would be off by that ratio unless students can be trained to automatically recalculate. But that means that even textbooks written by Martian scientists and educators will have to continue using Earth minutes, seconds, hours to avoid confusion.
  • Digital timekeeping would seem to allow Martians to use the same second, minute, and hour as we do on Earth, with the day flipping over at 24:39:35 instead of 24:00:00
  • The problem with this is that it would not allow time zones, in which, for communications purposes, every one has to have the same time plus or minus an integral number of hours.
  • The apparent solution is to have hourly adjustment - the hours would roll over at 61 minutes 1.65 seconds. This would allow broadcasts on the hour to begin simultaneously in different time zones e.g. at the top of the hour, at the half hour, etc. The advantage would be that the scientific second and minute would remain standard throughout the Solar System.
  • A better solution, offered as a friendly amendment to the original Zubrin proposal, is to adopt his 24:60:60 clock but give the slightly longer units different names so that there need never be any confusion:
  • EARTH Clocks: days - hours - minutes - seconds
  • MARS Clocks: sols - chrons - moments - tics
    Nb. "zonal", or simply "zones" taken from the time zones one "hour-like period" (1/24th day or sol apart.) would be an alternative to "chron". But with the adoption of "zode" for the month analog (see below), going with "zones" or "zonals" might be confusing.

The Week: this is a matter left unadressed in Zubrin's proposal

The 7 day week has been historically the most change resistant feature of our Calendars on Earth. Every attempt to shorten or lengthen the week has failed. Should we use the same names for the days of the week as we do on Earth, or their counterparts in another language? There is good reason not to do so:

  • It is the unspoken corollary of all Earth's religious fundamentalisms that the days of the week are a cosmic constant. When it is Sunday, it is Sunday throughout the Universe. But in fact, the 24 hour day which keeps the days of the week occurring "on schedule" is a purely local phenomenon on Earth.
  • On Mars, the day is somewhat longer, and in fact by the time 37 Earth days have lapsed, Mars has fallen a day behind. So even if we start out "Sunday here, Sunday there", in just a few weeks, Mars will be a day behind, and in a about eight Earth months, Mars will be a week behind.
  • Put it simply, Sundays, Mondays, Tuesdays, etc. are NOT cosmic, not even SOLAR System wide.
  • If we want a 7 day week, and that is a life rhythm deeply ingrained in all human cultures, it would be best to avoid confusion and pick an altogether different set of names.
  • Here are some suggestions
  • * The seven largest satellites in the Solar System: Ganymede, Titan, Callisto, Io, Luna, Europa, Triton in order of size - Luna could be confused with Monday but here it occurs in 5th spot instead of the 2nd. If alphabetical order were followed, Luna would again be fifth.
  • The seven largest volcanoes on Mars: Olympus, Ascraeus, Pavonis, Arsia, ?, ?, ?
  • Names of seven of Mars mythical-imaginary canals, as named by Lowell.
  • * The seven "Mercury" astronauts, in the order of their first flight: Shephard, Grissom, Glenn, Carpenter, Schirra, Cooper, Slayton - or in alphabetical order
  • NOTE: Already suggested (by Peter Kokh) for a proposed Lunar Calendar: The stars of the Seven Sisters or Pleiades: in alphabetical order these are: Alcyone, Asterope, Celaeno, Electra, Maia, Merope, and Taygeta (all Arabic names)
  • NOTE: Already suggested (by Peter Kokh) for a proposed Lunar Calendar: The seven major stars of the Big Dipper: Dubhe, Merak, Phad, Megrez, Alioth, Mizar, Alkaid (all Arabic names)
  • * Keep the present names (our Nordic or the Roman Classical set) but substitute -sol for -day, -tag, or dies, etc. Substitute Phobos for Moon (~Monday), Earth or Earth-Moon for Mars (~Tuesday) This has the two advantages of being easy to remember in the proper sequence, yet without confusion with the terrestrial days of the week.
  • See my alternative "Four Season Splityear Calendar for Mars" for yet another option, based on the familiar names for the notes of the diatonic musical scale.
  • Those suggestions that make use of familiar names* are in more keeping with Zubrin's precedent in choosing the familiar names of the twelve zodiac constellations for his "season-proportional" Martian "months" or "zodes".
  • Perhaps you can think of several more schemes - after all this is an arbitrary matter - then we could put it to a popular advisory vote among Mars Society attendees at the next convention.

The Month:

Zubrin divides the Martian year (I suggest the term "versary", from anniversary, to avoid confusion with standard Earth years) into twelve periods in which Mars travels equal 30 degree arcs of its orbit around the Sun. Because of Mars' considerable orbital eccentricity, in which it travels faster, covering the same 30 degrees in less days (or sols) when it is nearer to the Sun than when it is further out in its orbit, the twelve "zodiacal months" vary considerably in length. (I strongly urge the adoption of the word "zode" for these time periods. "Month" after all, refers to the "Moon", the satellite of Earth.)

Seasonal Color Key:

  • Northern Spring, Southern Fall
  • Northern Summer, Southern Winter
  • Northern Fall, Southern Spring
  • Northern Winter, Southern Summer
on Sol  
Gemini 1 - vernal equinox (N)


Leo 24 - Mars at aphelion
Virgo 1 - summer solstice (N)




Sagittarius 1 - autumnal equinox (N)
Dust storm season begins
Aquarius 16 - Mars at perihelion
Pisces 1 - winter solstice (N)
Dust storm season ends
Taurus 56 - Mars' New Year's Eve
  • This has the idyllic cultural advantage of better marking Mars all-relevant seasons, and of becoming one of the foundations of what is sure to emerge as a unique Martian culture by tying the zodiacal months or zodes tightly to the pace of the seasons.
  • This system would seem to have the strong accounting disadvantage of being "accounting-unfriendly" in the extreme. The businessman on Earth has enough trouble with the months varying from 28 to 31 days, a factor of about 10%. On Mars this variation would be much more pronounced with zodiacal months varying from 46 to 66 sols, a difference of 43 %, more than four times the variance we struggle with on Earth.
  • Conveniently, Mars "versary" is 96 7-sol weeks long. So most Mars Calendar-smiths divide that into 24 "months" each 28 sols or 4 weeks long precisely. This is convenient for bookkeeping.
  • But this is not the only possible bookkeeping solution. On Earth, "quarters" each 89-91 days or 3 months long, are the primary bookkeeping units. Taking that clue, the Martian versary, almost twice as long as our year, could be divided not into quarters, but into "eighths" or "octants", each (12) 7-sol weeks long or 84 sols apiece. Thus we could have a two tier way of dividing the Martian season-set or versary:
  • the " zodes" which accurately reflect Mars much more life-intrusive seasonal differences and thus underpin culture and holidays and festivals and the life-pace of how settlers adapt to their new home-world in general.
  • the "octants" (or accounting eighth parts of the calendar "versary", exactly 12 weeks long, divisible into thirds, exactly 4 weeks long for those who want to account on a shorter elapsed time basis. If printed calendar included a running number count of the weeks (1-96) this would help.
  • Since the twelve-week long eighths always begin on the same day of the week, this is a physical calendar-page-friendly solution. With this friendly amendment, we can wholeheartedly support Zubrin's zodiacal / "seasonal-month" plan.

Do we want a "traditional invariant week" Calendar that always starts on the first day of the week? On Earth, since there are not exactly 52 weeks in the year, the Calendar shifts one or two days each year, depending on whether or not that year is a leap year. Mars' "year" or "versary" is likewise a non-integral number of weeks long - 3 days shy of 96 weeks, to be exact.

But on Mars, where we are "starting over, starting fresh" we do not have the onerous burden of cultural inertia to overcome. The problem can be fixed.

I have laid out both options fully, "calendar page by calendar page" so you can see how the Mars Calendar would look on paper.


a Zubrin Calendar that starts on varying days of the week
a Zubrin Calendar that always starts on the 1st day of the week

  •   The Era:
    • Zubrin begins the Martian Era with the last occasion on which by happenstance, Mars Vernal Equinox, the logical time to begin its "year" or "versary" fell on our own January 1st. (1) By luck, that was in the year in which John F. Kennedy said humans would have a place beyond Earth orbit, the year when, after eons, Mars suddenly became a human destination, beginning with sorties to the Moon. (2) By using this coincidence, Zubrin sets up his "Areogator" for easy conversion of Earth dates to Martian dates and vice versa. The choice of any starting point other than one coincident with a January 1st date on Earth would not have allowed this. There are other reasonable starting points. But none of them offer this practical elegance. And who could argue with the time frame - the year when it first became "respectable" to think that humans would go to other worlds?
    • The one sticking point is that to distinguish the Earth year count from Mars year count, Zubrin uses Roman numerals (I, II, III etc.) for the latter, while we use Arabic numerals (1, 2, 3, etc.). Most educated persons can read Roman numerals - but for the majority of us, this "recognition" does not come with fluent rapidity. For Martian pioneers and students, this familiarity would soon come. For those who stay behind on Earth, however, this form of year reckoning may never become second nature. The insistence on use of Roman numerals would instead place a practical and cultural barrier in the way of hoped-for identification with the new Martian pioneers and their causes. Even for Martian students, calculating time spans by subtracting Roman numerals from one another will introduce unwelcome inconvenience in an already harsh environment.
    • Another way may be simply to use M.E. (Martian Era) after the Martian Year ("Versary") count given in familiar, arithmetically convenient Arabic numerals. Earth years can remain in A.D.
    • "A.D., Anno Domini = The Year of Our Lord = since the birth of Christ (apparently miscalculated and probably in 4, 5, or 6 B.C.) is rapidly becoming C.E. (Common Era) in the growing portion of the non-Christian world that has adopted western timekeeping for everyday affairs (while still using local calendars for cultural events, e.g. Chinese New Year.)
    • Yet another gimmick to differentiate the two time counts, would be to put the Martian "versary" count in brackets, e.g. 1 Gemini [37] - any notation but Roman numerals! Let's bear in mind that these nuances only exist in print. Orally, there is no difference between 3 and III, both commonly pronounced "three", unless we are now to start saying "I", "I", "I" instead of "3" and so on ? !

    Other Details:

    Details such as the manner of calculating leap years, are moot points, safely left up to committees.

    However, to keep the first of the year, and the first of each twelfthweek accounting period always on the first day of the week, any intercalary days / dates used to adjust accumulated fractions when they amount to an integral sol, should be "outside the week" e.g. "between Saturday and Sunday or their Martian equivalents, or "subtracting" a weekday that particular week, as the need may be (to add or subtract).

    A Summary Comparison - any school child can learn




















1.41 - 2.17





* NOTE: 36 Mars units (sols, chrons, moments, tics) = 37 Earth units


Main Menu
Pete's Mars Pages HOME
Re: Dr. Zubrin's
Mars Calendar
Ambitious Project Ideas
M.A.R.S. on Devon Island
Technologies Needed
Role of the Moon (IMHO)
Selected Mars Articles
Moon Miners' Manifesto
A Selection of Mars Links
& Other Mars Pages
Constructive Discuss
List on Project Ideas
Seeds of Martian Culture
One Way to Mars
Meeting Mars Halfway