Darian calendar

Darian calendar

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Encyclopedia
The Darian Calendar better known as the "Calendar of Adam" is a proposed system of time-keeping
Timekeeping on Mars
Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars.Mars has an axial tilt and a rotation period similar to those of Earth. Thus it experiences seasons of spring, summer, autumn and winter much like Earth, and its...

 designed to serve the needs of any possible future human settlers
Manned mission to Mars
A manned mission to Mars has been the subject of science fiction, engineering, and scientific proposals throughout the 20th century and into the 21st century...

 on the planet Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

. It was created by aerospace engineer
Aerospace engineering
Aerospace engineering is the primary branch of engineering concerned with the design, construction and science of aircraft and spacecraft. It is divided into two major and overlapping branches: aeronautical engineering and astronautical engineering...

 and political scientist
Political science
Political Science is a social science discipline concerned with the study of the state, government and politics. Aristotle defined it as the study of the state. It deals extensively with the theory and practice of politics, and the analysis of political systems and political behavior...

 Thomas Gangale in 1985 and named by him after his son Darius.

Year length and intercalation


The basic time periods from which the calendar is constructed are the Martian solar day (sometimes called a sol
Timekeeping on Mars
Various schemes have been used or proposed to keep track of time and date on the planet Mars independently of Earth time and calendars.Mars has an axial tilt and a rotation period similar to those of Earth. Thus it experiences seasons of spring, summer, autumn and winter much like Earth, and its...

) and the Martian vernal equinox year, which is slightly different from the tropical year
Tropical year
A tropical year , for general purposes, is the length of time that the Sun takes to return to the same position in the cycle of seasons, as seen from Earth; for example, the time from vernal equinox to vernal equinox, or from summer solstice to summer solstice...

. The sol is 39 minutes 35.244 seconds longer than the Terrestrial solar day and the Martian vernal equinox year is 668.5907 sols in length. The basic intercalation
Intercalation
Intercalation is the insertion of a leap day, week or month into some calendar years to make the calendar follow the seasons or moon phases. Lunisolar calendars may require intercalations of both days and months.- Solar calendars :...

 formula therefore allocates six 669-sol years and four 668-sol years to each Martian decade. The former (still called leap years
Leap Years
Leap Years is a 2001 drama television series that aired on the Showtime cable network. The show was created by Ron Cowen and Daniel Lipman, who had created the American version of the series Queer as Folk. It followed a group of friends in New York City...

 even though they are more common than non-leap years) are years that are either odd (not evenly divisible by 2) or else are evenly divisible by 10. The calendar error from the actual seasons is small, but the calendar is too slow by about 13 sols every 1400 Martian tropical years.

Calendar layout


The year is divided into 24 month
Month
A month is a unit of time, used with calendars, which was first used and invented in Mesopotamia, as a natural period related to the motion of the Moon; month and Moon are cognates. The traditional concept arose with the cycle of moon phases; such months are synodic months and last approximately...

s. The first 5 months in each quarter have 28 sols. The final month has only 27 sols unless it is the final month of a leap year when it contains the leap sol as its final sol.

The calendar maintains a seven-sol week
Week
A week is a time unit equal to seven days.The English word week continues an Old English wice, ultimately from a Common Germanic , from a root "turn, move, change"...

, but the week is restarted from its first sol at the start of each month. If a month has 27 sols, this causes the final sol of the week to be omitted. This is partly for tidiness. It can also be rationalised as making the average length of the Martian week close to the average length of the Terrestrial week, although it must be remembered that 28 Earth days is roughly equal to 27+1/4 Martian sols and not 27+5/6 Martian sols.

In the following table, the days of the week are Sol Solis, Sol Lunae, Sol Martius, Sol Mercurii, Sol Jovis, Sol Veneris, Sol Saturni.
Sagittarius   Dhanus   Capricornus
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28
         
Makara   Aquarius   Kumbha
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27  
         
Pisces   Mina   Aries
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28
         
Mesha   Taurus   Rishabha
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27  
         
Gemini   Mithuna   Cancer
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28
         
Karka   Leo   Simha
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27  
         
Virgo   Kanya   Libra
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28
         
Tula   Scorpius   Vrishika
So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa So Lu Ma Me Jo Ve Sa
1 2 3 4 5 6 7 1 2 3 4 5 6 7 1 2 3 4 5 6 7
8 9 10 11 12 13 14 8 9 10 11 12 13 14 8 9 10 11 12 13 14
15 16 17 18 19 20 21 15 16 17 18 19 20 21 15 16 17 18 19 20 21
22 23 24 25 26 27 28 22 23 24 25 26 27 28 22 23 24 25 26 27 28


The last day of Vrishika is an intercalary day that does not occur in every year.

Start of year


The Martian year is treated as beginning near the equinox
Equinox
An equinox occurs twice a year, when the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the center of the Sun being in the same plane as the Earth's equator...

 marking spring in the northern hemisphere of the planet. Mars currently has an axial inclination
Axial tilt
In astronomy, axial tilt is the angle between an object's rotational axis, and a line perpendicular to its orbital plane...

 similar to that of the Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, so the Martian seasons are perceptible, though the greater eccentricity of Mars' orbit about the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 compared with that of the Earth means that their significance is strongly amplified in the southern hemisphere and masked in the northern hemisphere. The most sophisticated calculations of the Darian calendar extend to the point of making allowance for the slight increase in the length of the Martian vernal equinox year over several thousand years. These prescribe a more complicated intercalation formula (for details see the link cited below).

Epoch


Gangale originally chose late 1975 as the epoch
Epoch (reference date)
In the fields of chronology and periodization, an epoch is an instance in time chosen as the origin of a particular era. The "epoch" then serves as a reference point from which time is measured...

 of the calendar in recognition of the American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 Viking program
Viking program
The Viking program consisted of a pair of American space probes sent to Mars, Viking 1 and Viking 2. Each spacecraft was composed of two main parts, an orbiter designed to photograph the surface of Mars from orbit, and a lander designed to study the planet from the surface...

 as the first fully successful American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 soft landing mission to Mars and ignoring the earlier 1971 Soviet Mars 3
Mars 3
The Mars 3 was an unmanned space probe of the Mars program, a series of unmanned Mars landers and orbiters launched by the Soviet Union in the early 1970s....

 Landing. In 2002 he adopted the Telescopic Epoch, first suggested by Peter Kokh, which is in 1609 in recognition of Johannes Kepler
Kepler's laws of planetary motion
In astronomy, Kepler's laws give a description of the motion of planets around the Sun.Kepler's laws are:#The orbit of every planet is an ellipse with the Sun at one of the two foci....

's use of Tycho Brahe
Tycho Brahe
Tycho Brahe , born Tyge Ottesen Brahe, was a Danish nobleman known for his accurate and comprehensive astronomical and planetary observations...

's observations of Mars to elucidate the laws of planetary motion, and also Galileo Galilei
Galileo Galilei
Galileo Galilei , was an Italian physicist, mathematician, astronomer, and philosopher who played a major role in the Scientific Revolution. His achievements include improvements to the telescope and consequent astronomical observations and support for Copernicanism...

's first observations of Mars with a telescope
Telescope
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation . The first known practical telescopes were invented in the Netherlands at the beginning of the 1600s , using glass lenses...

. Selection of the Telescopic Epoch avoids the problem of the many telescopic observations of Mars over the past 400 years being relegated to negative dates.

Nomenclature


Suggested variations of the Darian calendar abound on the World Wide Web that use different nomenclature schemata for the days of the week and the months of the year. The names of the 24 months were provisionally chosen by Gangale as the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 names of constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....

s of the zodiac
Zodiac
In astronomy, the zodiac is a circle of twelve 30° divisions of celestial longitude which are centred upon the ecliptic: the apparent path of the Sun across the celestial sphere over the course of the year...

 and their Sanskrit
Sanskrit
Sanskrit , is a historical Indo-Aryan language and the primary liturgical language of Hinduism, Jainism and Buddhism.Buddhism: besides Pali, see Buddhist Hybrid Sanskrit Today, it is listed as one of the 22 scheduled languages of India and is an official language of the state of Uttarakhand...

 equivalents in alternation. The 7 sols of the week, similarly, were provisionally named after the Sun, Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 and the 5 brightest planets as seen from Mars — including Earth. The Darian Defrost Calendar, for instance, creates new names for the Martian months out of patterns relating letter choice and name length to month order and season. The Utopian Calendar, devised by the Mars Time Group in 2001, has additional suggestions for nomenclature modification.

Martiana Calendar


In 2002 Gangale devised a variant of the Darian calendar that reconciles the months and the sols of the week in a repeating pattern and removes the need to omit days of the week. In the Martiana variant, all the months in a given quarter begin on the same sol of the week, but the sol that begins each month shifts from one quarter to the next.

The following table shows the sol of the week on which each month in the quarter begins. The first quarter corresponds to spring in the Martian northern hemisphere and autumn in the Martian southern hemisphere.
  First quarter Second quarter Third quarter Last quarter
Even-numbered years Sol Solis Sol Saturni Sol Veneris Sol Jovis
Odd-numbered years Sol Mercurii Sol Martis Sol Lunae Sol Solis


The leap sol occurs at the end of odd-numbered years as in the original Darian calendar. Since the last month of odd-numbered years contains 28 sols, the following year also begins on Sol Solis, resulting in a two-year cycle over which the relationship of the sols of the week to the months repeats. The sol that is added every tenth year is epagomenal (not counted as part of the week), thus the two-year rotation of the sols of the week is not disrupted. The Martiana scheme avoids the Darian calendar's need to shorten the week to six sols three to four times per year. The disadvantage is that the scheme results in a two-year cycle for reconciling the sols of the week and the months, whereas the Darian calendar is repeatable from month to month.

Other Darian calendars


In 1998 Gangale adapted the Darian calendar for use on the four Galilean moons of Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...

 discovered by Galileo in 1610: Io
Io (moon)
Io ) is the innermost of the four Galilean moons of the planet Jupiter and, with a diameter of , the fourth-largest moon in the Solar System. It was named after the mythological character of Io, a priestess of Hera who became one of the lovers of Zeus....

, Europa
Europa (moon)
Europa Slightly smaller than Earth's Moon, Europa is primarily made of silicate rock and probably has an iron core. It has a tenuous atmosphere composed primarily of oxygen. Its surface is composed of ice and is one of the smoothest in the Solar System. This surface is striated by cracks and...

, Ganymede
Ganymede (moon)
Ganymede is a satellite of Jupiter and the largest moon in the Solar System. It is the seventh moon and third Galilean satellite outward from Jupiter. Completing an orbit in roughly seven days, Ganymede participates in a 1:2:4 orbital resonance with the moons Europa and Io, respectively...

, and Callisto
Callisto (moon)
Callisto named after the Greek mythological figure of Callisto) is a moon of the planet Jupiter. It was discovered in 1610 by Galileo Galilei. It is the third-largest moon in the Solar System and the second largest in the Jovian system, after Ganymede. Callisto has about 99% the diameter of the...

. In 2003 he created a variant of the calendar for Titan
Titan (moon)
Titan , or Saturn VI, is the largest moon of Saturn, the only natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found....

.

External links