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


A Four Season Split-year Calendar for Mars
The Mars Pulse Calendar"
The "Mars Human Heritage" Epoch

.........[version 11/07F]

Calendar Design Goals:

Even # of "same length" Months

Integral sets of months per Season.
Mars seasonal patterns will insinuate themselves strongly into all aspects of Martian life and culture. It will be ideal if they each begin at the beginning of a month. If we want our months to vary as little as possible in length,. this is a challenge, because, owing to Mars' very eccentric orbit, the seasons themselves vary greatly in length - (local Martian days or "sols")

  • 192 days Northern Spring / Southern Autumn
  • 180 days Northern Summer / Southern Winter
  • 146 days Northern Autumn / Southern Spring
  • 150 days Northern Winter / Southern Summer

    Two 334 day half years.
    This will allow celebrations and observances on a schedule much closer to the length of the familiar Earth year (365 days) instead of the 668 sol long Martian year. At the same time, we could choose to celebrate some events (those taking place on Mars) on a long year schedule. This option would make it easier for religious traditions to translate their feast and holy day schedule, easier for sports teams to cycle their seasons, and easier for schools to schedule their very long Mars year need not take as much getting used to as we thought. While the cycle of the seasons IS long, the cycle of human activities could be shorter, precisely on a 2:1 scale.

  • Note: We would still count Mars Years as always, one every 668.6 sols; it is just "versaries" that we propose to count by the half year. So this system would not affect the way we calculate the Mars epoch count or transpose Earth Common Era dates.

    Perpetual dating,
    .....Dates falling on the same week day each full year.

    Equal length accounting periods of integral number of weeks

    Month names with some of these features

  • Some connection with Mars: mythological, historical, astronomical, etc.
  • If we are going to have two half-years repeating many observances, then we really need two sets of basically the same names, possibly with slight differences to denote the half year in which they fall. This would tend to rule out references to the constellations of either the ecliptic (Zodiac) or of Mars' celestial equator.
  • They should not incorporate names cognate with the month names in our own calendar. That would cause confusion. Nor would they offer a clue to the season, if we are cycling the names twice a full 4-season year.

    A Seven Day Week.
    we could experiment with weeks of other lengths (9, 10, 11 days) in various settlements to see if they catch on. But most people are familiar and comfortable with the seven day rhythm. There will be enough necessary innovation on Mars. Adding gratuitous innovation will make adjustment more difficult. Further, most of the major religious traditions would want to keep the seven day rhythm as their religious observances are keyed to such a sequence. As 37 Earth days will cycle in the same time as 36 of the longer Mars days, there is no way for the days of the week to keep pace with one another on the two worlds, unless one Mars week day is skipped every 5 weeks or so. Neither Sundays or Saturdays are cosmos wide. Therefore:

  • The names of Martian weekdays should be different, so as to avoid unnecessary confusion.
  • Earth weekdays are named after the seven brightest moving objects in the sky: Sun, Moon, Mars (Tiu), Mercury (Woden), Jupiter (Thor), Venus (Fria), and Saturn. The origin of this system is based on astrology, however, not astronomy. If we were to adopt the same system, we would want to substitute Phobos for Moon, Earth for Mars. Then, to avoid confusion, we would have to change the suffix -day to something else.
  • The seven great moons of the solar system: Ganymede, Titan, Callisto, Io, Luna, Europa, Triton
  • Some other worthy set of seven names - note that the weekdays cycle, repeating on the octave. On Earth, Saturday immediately "demands" in our mind to be followed by Sunday out of constant association. A new set of names would not automatically "recycle" in our minds without some repetition.



The "Mars Pulse" Calendar

First, these changes in terminology:
The Seasons are introduced by Equinoxes ("Vernal" Equinox introduces Spring while the "Autumnal" Equinox introduces Fall or Autumn) and by Solstices ("Summer" and "Winter"). At the equinox, the Sun is over the equator and the days and nights are of equal length. From this moment, it moves either north or south and the days grow longer as the nights grow shorter in one hemisphere, just the opposite in the other. At the solstices the Sun is at maximum latitude either north of the equator or south of it, and in one hemisphere the days are at their longest while the nights are at their shortest. Meanwhile the opposite is the case in the other hemisphere. The problem is that we traditionally name the equinoxes and solstices by the season that they introduce in the northern hemisphere. To people in the southern hemisphere, these chauvinism makes no sense. Nor, for all its many-centuries long ingrained tradition, is it necessary. Instead, we urge the adoption of new names for the equinoxes and solstices, and for the planet wide seasons that they introduce. It is time, as we set out to settle a brand new world, to leave these unnecessary chauvinisms behind.

  • Northward Equinox - introducing Spring (Latin Vernes) in the North, Autumn in the South - so we can call this planet wide season Vertum
  • Northern Solstice - introducing Summer in the North, Winter in the South - so we can call this planet wide season Sumwin
  • Southward Equinox - introducing Autumn in the North, Spring (Vernes) in the South - so we can call this planet wide season Tumver
  • Southern Solstice - introducing Winter in the North, Summer in the South - so we can call this planet wide season Winsum


An even number of months
....of comparable length integral number for each season.
  • Richard Weidner's 22 month scheme comes close.
    [The calendar of the Reverend Fred Allan Hightower (Bubba <>) also has 22 months but they are not rationalized (yet) to the pace of the seasons.]
    Here is Weidner's system:
    • Vertum 192 - 6 months 32 days each
    • Sumwin 180 - 6 months 30 days each
    • Tumver 146 - 5 months (4 of 29, 1 of 30)
    • Winsum 150 - 5 months 30 days each
  • Note that Sumwin and Tumver total 11 months of 326 days
  • Note that Winsum and Vertum total 11 months of 342 days
  • If we average Tumver and Winsum to 148 days each (2 at 29, 3 at 30) that means starting Winsum 2 days before the Southern Solstice, but leaving Vertum to begin right on the Northward Equinox.
  • If we average Vertum and Sumwin to 186 days each (6 at 31) that means starting Sumwin 6 days before the Northern Solstice, but leaving Tumver to start on time with the Southern Solstice.
  • If we now start the year with Winsum (northern winter, southern summer) instead of Vertum (Vernal Equinox: northern spring, southern autumn) we end up with two eleven month half years precisely 334 days long.
  • The two eleven month sequences are mirror images:
    Winsum /
    Vertum 29, 29, 30, 30, 30, 31, 31, 31, 31, 31, 31
    Sumwin / Tumver 31, 31, 31, 31, 31, 31, 30, 30, 30, 29, 29
    Winsum / Vertum begins 38 days after perihelion and is basically the "outbound leg" of Mars' orbital year
    / Tumver is basically the "inbound leg" of Mars' orbital year.
    Facts illustrated in the color graphic border, left
    • Note that the north and south seasons are opposite, sequencing in offset manner, as on Earth
    • Note how logical the naming system is for planet-wide season. Note the color match of the season name roots: Win (white - winter), Sum (darker green of summer), Ver (lighter green of spring), Tum (fall colors of autumn leaves). Each name tells instantly what season is underway in which hemisphere.
    • The blue shading denotes the reduced solar input as Mars is near aphelion, its furthest distance from the Sun.
    • The inward and outward cycling of Mars in its eccentric orbit about the Sun is also indicated by the thin rainbow stripe.
    • The pink horizontal line divides the two equal "half years", or "semi years", or "splits"
    • The horizontal red line marks the point at which one full Mars long year ends, and the next begins.


    Two sets of 11 Month Names each

  • I tried a couple dozen variations, all using the most common root in our present list of 12 Earth month names: "ber" [September, October, November, December] After multiple comparisons, I narrowed my choice to two proposals. Both incorporate the mnemonic principal of alphabetical "AB to K" order. This not only makes them easier to learn and remember, but makes possible "one character notation" (i.e. M not MM)
  • The first proposal adds no further elements:
    A'ber - B'ber - C'ber - D'ber - E'ber - F'ber - G'ber -H'ber - I'ber - J'ber - K' ber
    The same sequence months in alternating two half year sequences (or "splits") would be distinguished from one another by adding 1 or 2 after the month names: The dates would precede the month name in European style - e.g. 31 K'ber 1 is followed by A'ber 2 and 29 K'ber 2 by 1 A'ber 1.
  • The second proposal is more elaborate, with each month name beginning and ending with the opposite letters (A-K + K-A): i.e..
    AK, BJ, CI, DH, EG, FF, GE, HD, IC, JB, KA.
    names of the outbound leg half year are distinguished from those of the inbound leg by reversing the consonants of the root ber, the vowel e omitted: br and rb. This works well because r is a liquid, so the combination br and rb are pronounce with equal ease, there being a vowel both before and after. The choice of the first vowel is dictated by the sequence a-e-i-o-u being followed as far as it can re-starting with the vowel of each month beginning with a vowel. Thus
    Bej, CiI, DoH, EG, FiF, GoE, HuD, IC, JoB, KuA.
    [As luck would have it, we have i following C which makes it soft and distinguishable phonetically from K. And also by luck we have o following G which makes it hard, as soft G would be pronounced like J.]
    Next we add the root br (for the first set, rb for the second) and the opposite sequence of vowels. The result is two sets of month names. Those of the alternating set turn out to be exact mirror images of the first step in reverse order. However, to prevent


    "br" series - outbound

    "rb" series - inbound
























  • Note that the first letter is A to K in sequence, while the last letter is K to A in sequence
  • The first vowel sequence is AeioEiouIou, where the last letter sequence is uoiuoieoiea, the exact reverse order.
  • The first month outbound, Arbuk, is the phonetic opposite of the last month inbound, Kurba and so on.
  • The first name proposal (A'ber) is simpler and easier to remember, but needs a qualifying halfyear number.
  • The second name proposal (Arbuk) is more elegant and logical in that the names mirror one another in reverse sequence suggesting equivalent inbound and outbound positions as well as 1-11 sequence, and also by incorporating the distinction between outbound and inbound months in the labial/liquid [br] - liquid/labial [rb] reverse consonant root combinations. It will be harder to learn initially, but has these two advantages:
    • The names follow immediately from a few principles with no arbitrary additions, unlike Frans Blok's Rotterdam name set.
    • The names have an unearthly yet easily pronounceable ring to them, something that will lend them well to a distinctively Martian ambiance.
  • I have no present preference for either of these two name proposals, but introduce them both. It will be interesting to see which is more popular in the short run, and which more popular in the long run.


A Fresh Set of 7 Weekday Names
  • The seven notes of the diatonic musical scale, recycling on the octave, are an ideal model: do, re, mi, fa, so[l], la, ti, (do).
  • As to the suffix -day, its replacement by -sol referring to the Sun has the problem that the sol is the generic name for the rotations of all bodies in the solar system. If we do not want to use -day because we reserve it for the Earth period, then we ought not to use the generic -sol for the Mars rotational period, as that would rob it of its useful generic currency. What we are trying to name is the period from local midnight to local midnight centered around sunrise-noon-sunset. So I suggest we use -noon as the suffix. It's familiar and instantly significant. (And it has that "Barsoomian" feel to it!) Our Weekday names are then:
  • Donoon - Minoon - Renoon - Fanoon - Sonoon - Lanoon - Tinoon.
    sequence is instantly clear and transparent and so easy to remember that you can sing it. The initial vowels keep their familiar Latin - Italian sonorous value (doh, ray, mee, fah, soh, lah, tee).


A Better Perpetual Calendar
  • The Martian year, if we use 7 day weeks, has 95 weeks and 3 days left over - 4 days shy of 96 weeks. 96 is an ideal number as it is divisible by 12, 8, 6, 4, 3, and 2. If we include in our calendar a running count of the weeks, this number appearing in the Donoon (~Sunday) box, then we can divide the full Martian long year into (8) 12-week periods for accounting purposes, each 84 days long - not that incommensurable with our own 91 day quarters.
  • Now to reset the weekdays so that the first day of each year begins with Donoon, we have to drop 3 or 4 weekdays the 96th week of the year - Unless ...
  • If we have the split year system, and want to start each half year on Donoon, we have only to drop 1 or 2 weekdays from the 48th week. That drastically halves the reset glitch and whatever pain it causes. Religious leaders will know that their favored day of rest comes one or two days earlier that week, not later, and that they may see as a good thing.
  • With a perpetual calendar, it will be much easier to establish both holy days and holidays so that they fall on the desired weekday or weekend day.
  • As to the complaint "my birthday always falls on a Fanoon" the answer is easy. You can celebrate it on whatever weekend date, before or after, suits you, if that's what you want. It is more important to schedule public celebrations on weekend days or the day before or after (Lanoon, Tinoon, Donoon, Minoon).


Leap Year Systems
  • While a leap year system is important, it is quite an independent issue with little or no relation to the internal structure of the calendar and the way Mars Time is divided into ergonomic, human-scale intervals. Accordingly, I defer this essentially technical question.
  • There are two systems on the table: that of Richard Weidner and that of Tom Gangale. Both are accurate over the long period. Gangale's is easier for the common layman to understand and keep track of. To me, it is not necessary to be track the exact ideal starting moment of the year any more closely than has the Gregorian / Common Era calendar in virtually global use on Earth.
  • The Mars Pulse Calendar follows the Mars "Tropical" Year. Our Earth Calendar follows Earth's Sidereal Year. The difference will not be apparent for many generations. It is more important for the purposes of human life on Mars top have a season-based tropical year, whether astronomers living on Earth like it or not.
  • No one will die or suffer or be in any real way inconvenienced or endangered if the northward (vernal) equinox now and then falls on the last day of Winsum or the second day of Vertum, instead of on the first of Vertum. The simpler Blok leap year reckoning formulas suit me just fine.


The Epoch Question

When should we date Mars Year 1? Some people want Mars Year 1 to mark a watershed event in the recent past or near future. There is great disagreement on which event to pick.

  • Arrival of first intact human artifact on Mars - Mars 3 Lander (USSR) 12/2/71
  • Arrival of first human probe to land on Mars and send back data - Viking I (USA) ../1976
  • Start of the Founding Mars Convention in 1998 (this was a restart. There has been a significant pro-Mars community for many years. To choose the 1998 event, as important a revival as it was, would be an insult to many)
  • Mars Landing Day of the first human expedition. The disadvantage of this is that since we cannot even guess intelligently when that will be, we loose the publicity and educational outreach value of having a Mars Calendar NOW.

    I prefer a "Mars Human Heritage Epoch" system that goes "way, way back" to a calculated year 1 start date that would include most "datable" significant events in human history in positive numbers -- i.e. a 1 ME that goes back toward the beginning of the 2nd Millennium BC or even further back. While Mars is a fresh, raw, untouched world, the Pioneers will not be "fresh" -- they will bring with them, for good or ill, the baggage of millennia of human heritage. Even if they think at first that they are starting totally afresh, in time Martians will come to realize that Earth's ancient history is Mars' ancient history also. Two suggestions:

  • Set 2001 ME to be roughly concurrent with 2001 CE
    That would put year 1 ME back in the 18th century BC and include much of the really significant events and developments of ancient Phoenicia, Greece, Rome, Crete, Troy, Egypt, Mesopotamia, Persia, India, and China in a current Human Heritage era. Such a "co-callibration of the Earth and Mars Epochs would make easier "back of the envelope" date conversions. That it doesn't matter to computers is a very snobbish and elitist viewpoint. There still are, and always will be, humans who do their math themselves.
  • Make use of the retro-calculated Julian Day 1 (January 1, 4713 B.C.) to set Mars Human Heritage year 1, even further back. That would make it currently about ME 3308.