The Areosynchronous Calendar

Credits/References

This calendar was constructed using contributions from the following people:

• Tom Gangale - the Darian Calendar
• NASA JPL Viking mission team - the term 'sol'
• Peter Kokh - names for Martian seasons (from the Mars Pulse Calendar)
• Frans Blok - the Rotterdam system for naming Martian months
• Shaun Moss - the term 'mir' and names for sols-of-the-week (source = here)

If you have, or know of, a brilliant idea that you think should be a part of the Areosynchronous Calendar, please email me.

Terminology

I have chosen to adopt the names of the seasons proposed by Peter Kokh (author of the Mars Pulse Calendar and Prospector Pete's Mars Pages). The problem with using the familiar terms 'Spring', 'Summer', 'Autumn', and 'Winter' is that these terms refer to a different time of year in the Northern versus the Southern hemisphere - for example, it is Spring in the North while it is Autumn in the South and vice-versa. Peter has invented new names for the Martian seasons that can be used planet-wide. Note that the term 'Vernes' is used in place of 'Spring' - this is the Latin equivalent from which the word 'vernal' is derived, as used in 'vernal equinox'.

As you can see, Mars' seasons are not of equal length - this is because of Mars' elliptical orbit.

How does a mir align with the seasons? Although the Gregorian calendar does not begin on a seasonal marker (that is, a solstice or equinox), the convention in both astronomy and astrology is to mark the beginning of a year with the Northern Vernal Equinox. This approach has naturally been popular in the design of Martian calendars too, and as there are no reasons to oppose this choice, the Areosynchronous Calendar also begins each mir with the Vertum Equinox.

Month lengths

The system of month lengths described by the original Darian calendar offers several compelling features, the most important of which is that it is easy to understand: A mir of 668 sols is divided into 4 quarters of 167 sols, each of which is further divided into 6 months - 5 months of 28 sols plus one month of 27 sols. The number of months therefore totals 24. In a leap mir the final month has an extra sol, totalling the usual 28.

Here are the advantages of this system:

• Each quarter is the same length of 167 sols, except for the final quarter in a leap mir which has 168 (compare with Earth/Gregorian where quarters may be 90, 91 or 92 days).
• All months have a consistent length of 28 sols, except for 3 or 4 per mir which have 27. These 'clipped' months are evenly spaced and always occur at the end of a quarter.
• 24 is a useful number of months, as it then becomes simple to divide a mir into 2, 3, 4, 6, 8, or 12 equal parts.
• 27 or 28 sols is approximately the same duration as a Gregorian calendar month (27.25 .. 30.17 sols) or Lunar month (28.74 sols). Considering future interplanetary commerce between Mars, Luna, and Earth, it will be useful for a month to mean approximately the same thing on each world. Months of this length are also more harmonious with the female menstrual cycle.
• The extra sol in a leap mir is the last one of the mir. This is more convenient, and after all, if you want an extra free sol, New Mir's Eve would be the best time to have it!

This arrangement of months is expressed diagrammatically below, along with their names.

Month names

For the month names I have adopted the Rotterdam system (recommended reading) by Frans Blok (author of Frans Blok's Earth2Mars pages). Frans has invented original names for the Martian months using clever patterns of vowels and consonants, and I perceive this to be the least culturally-biased and most creative proposal:

There are a number of patterns contained within the arrangments of letters used to make each name. These are described better on Frans' website, so please take a look, but here they are in brief:

• Each month begins with a consecutive letter of the alphabet (only Q and Y are omitted). This means that if a month comes later in the alphabet, it comes later in the mir. Also a month can easily be abbreviated to a single letter, which is very convenient for writing dates.
• The last letters of each month follow a pattern of 'R', 'A', 'N', 'I', 'L', 'O'. This means that you can always tell what position a month is within a quarter-mir by looking at the last letter. A clipped month always ends in an 'O'.
• Odd months end in consonants, even months end in vowels.
• If a month name other than Deti contains a 'D', then it's the first in a group of four.

The names also correspond to Mars' variable-length seasons:

• Names containing a 'U' (Neturima to Zungo, 11 months), indicate a Tumver or Winsum month.
• Names of 3 or 4 characters (Adir to Geor, 7 months) indicate a Vertum month. The regular months of 28 sols have 4 letters and 2 syllables in their names, the clipped month, Flo, has 3 letters and 1 syllable.
• Names with 5 or 6 letters, not containing a 'U' (Heliba to Medior, 6 months) indicate a Sumwin month. The regular months have 6 letters, 3 syllables, the clipped one, Larno, has 5 letters, 2 syllables.
• Names with 7 or 8 letters (Neturima to Safundo, 5 months) indicate a Tumver month. The regular months have 8 letters, 4 syllables, the clipped one, Safundo, has 7 letters, 3 syllables.
• Names with 5 or 6 letters, containing a 'U' (Tiunor to Zungo, 6 months) indicate a Winsum month. The regular months have 6 letters, 3 syllables, the clipped one, Zungo, has 5 letters, 2 syllables.

Week lengths

The 7-day week dates back to ancient Mesopotamia, however, there have been several attempts by different leaders to introduce weeks of different lengths (anywhere from 4 to 10 days). These attempts have all been eventually abandoned due to lack of acceptance. For some mysterious reason, human society seems to naturally prefer a 7-day work-rest cycle.

The 7-day week is used worldwide, and, as this is one of the few aspects of society that almost all humanity agrees on, many designers of Mars calendars have felt it prudent to similarly define a Martian week to be 7 sols. Another minor advantage to implementing a 7-sol Martian week is that the term 'fortnight', meaning 'fourteen nights', will continue to equal two weeks.

Names for sols-of-the-week

After examining the many different Martian calendars, I hadn't found a set of names for the sols that I really liked, so I've opted to make up my own. Before naming the sols in the Martian week, it is worthwhile to investigate how our current days of the week got their names.

According to several sources, including this informative web page, the days of the week were named by Persian astrologers for the 7 known celestial objects - the Sun, Moon, and the five planets known at that time. The Egyptians also adopted this system, followed by the Hebrews, Arabs, Indians, Tibetans, Burmese, and Japanese. Here we have yet another curious mystery surrounding the week - not only the system of 7 days per week, but the system of naming them was adopted almost unanimously by vastly different cultures worldwide. Even the order in which the days were named was preserved - the first day named for the Sun, followed by the Moon, Mars, Mercury, Jupiter, Venus, and Saturn.

This system of assigning the days of the week to celestial bodies is still accepted worldwide and, similarly to the 7-day week, there aren't valid reasons to deviate from it. Therefore, I've also adopted an astrological approach and named each sol of the week after the 7 most astrologically significant celestial objects in the Martian sky - the Sun, the two Martian moons, and the 4 planets closest to Mars: Earth, Venus, Mercury, and Jupiter.

One of the advantages of this set of names is that they each begin with a different letter, which makes for easy abbreviations. [If you're wondering where the new names for the Martian moons came from, please read The Renaming of Mars' Moons.]

Weekends

The story goes that "the LORD made the heavens and the earth, the sea and all that is in them, and rested on the seventh day; therefore the LORD blessed the sabbath day and made it holy". The Hebrews were instructed by Moses that it was forbidden to work on the Sabbath, the last day of the week, which was to be set aside for religious observances.

Sun-worshipping pagans, however, considered the 'day of the Sun' to be their holy day (holiday). The Roman Catholic church changed the Christian holy day to Sunday around 1000AD, as a means of marketing Christianity to pagan cultures. Many western religious groups have since followed suit.

Society is adaptable, and as we know, in modern times most people have both the first and last days of the week free. The system of having these two holidays per week is in widespread usage by people of all cultures, and I suspect most would be happy to continue this pattern on Mars. Hence, a typical Martian working week in the Areosynchronous Calendar is from Neriosol to Mercusol, and the weekend is Jovisol and Heliosol.

Synchronization of weeks and months

The choices made regarding month and week lengths result in an attractive feature that our Earthly Gregorian calendar does not have. Most of the Martian months contain 28 sols - exactly 4 weeks per month - therefore a month can easily and conveniently be divided into 2 fortnights or 4 weeks.

Imagine for a moment that every month in our new Martian calendar contained 28 sols - another useful advantage would emerge, namely that each month would begin on the same sol of the week. By starting a mir on the first sol of the week, the first sol of each month would therefore also fall on the first sol of the week. This would result in the useful situation that each calendar page would look pretty much the same (as will be presently illustrated).

Simplicity is a virtue in any system, and this is especially true in the case of a major societal system such as a global calendar. This kind of synchonization between the weeks and months means that determination of the sol of the week from the date becomes trivial. For example, if our Gregorian Calendar had this feature, the first day of any month would be a Sunday - as would the 8th, 15th, and 22nd.

However, we have an unresolved issue - not all months in the Darian calendar have 28 sols - every 6th month (except for Zungo in leap mirs) is a clipped month with 27 sols. Thus, if we maintained our familiar 7-sol cycle, we would lose synchronization by one sol per quarter-mir. The first 6 months would begin on the first sol of the week, the second 6 months would begin on the 7th sol of the week, the third 6 months would begin on the 6th sol of the week, and so on.

The Darian calendar proposes that, in order to take advantage of the benefits inherent in synchronization of weeks and months, we begin each month with the first sol of the week anyway, which means skipping the last sol of the final week in a clipped month. The final week of a clipped month therefore contains only 6 sols - a 'clipped' week.

Will this work? As we've noted, humans have historically not conformed to weeks of any length other than 7 days. Considering, however, that Martians will not be ordinary humans, but will in fact be highly adaptable and mentally acute people living in unusual conditions, I expect that this clipped week will actually prove to be one of the easier things for us to accept.

To summarize: the Darian calendar synchronizes the weeks and months in the following way - most months contain 28 sols, which is exactly 4 weeks of 7 sols, whereas the few clipped months per mir containing 27 sols are comprised of 3 regular 7-sol weeks and one clipped week of 6 sols. Hence, each month, and correspondingly, each mir, begins on the first sol of the week. This results in an extremely useful feature that an Earth calendar has never had - the name of the sol can always be easily deduced from the date, regardless of month or mir.

Here is the calendar page for any regular 28-sol month. Note the convenience of abbreviating the sol names to a single letter. Holisols are shown in light blue: