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The Davidian Martian Calendar is a proposed system of time-keeping designed to serve the needs of future human settlers on the planet Mars. It was established by David Powell in Gregorian Year 1988. In 1996, a system of converting dates between Gregorian and Davidian calendars was created.

Calendar TermsEdit

The Davidian calendar uses the same terminology as that used by the Gregorian calendar:

Minute: Period of 60 Martian seconds (61.62s on Earth).

Hour: Period of 60 Martian minutes (61m 38.968s on Earth).

Day: Period of 24 Martian hours (24h 39m 35.244s on Earth).

Week: A period of 10 days.

Month: A unit of time that on Mars simply means 1/12 of a year.

Year length and intercalationEdit

The Martian year is 669.5907 Martian days long. Therefore, with very rare exceptions, every century must have 59 leap years. That means that unlike on Earth, leap years are actually more common than "common" years.

Leap years are as follows:

  • Every even numbered year except for those that end in "00"
  • Every odd-numbered year that is evenly divisible by 5: 05, 15, 25, 35, 45, 55, 65, 75, 85, 95

Additionally, years that end in 0000, 2000, 4000, 5000, 6000, 8000, and 9000 begin with a January 0 or "Millennium Day" that does not belong to any day of the week.

Calendar LayoutEdit

The year is divided into 12 months. The months of January through June have 50 days, while July through December have 60 days. In addition, two holiday weeks of 4 or 5 days at the end of June and 5 days at the end of December is added to equal 669 or 670 days, depending on leap year. This keeps the calendar perpetual.

There are ten days per week, named after astronomical phenomena as seen from Mars, to follow the tradition of the Earth Gregorian calendar: Sunday, Phoboday, Deimoday, Wednesday, Thursday, Friday, Saturday, Uranuday, Neptday, and Teraday.

January   February   March
Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50
         
April   May   June
Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50
51 52 53 54 55*
   
July   August   September
Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60 51 52 53 54 55 56 57 58 59 60 51 52 53 54 55 56 57 58 59 60
   
October   November   December
Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter Sun Pho Dei Wed Thu Fri Sat Ura Nep Ter
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60 51 52 53 54 55 56 57 58 59 60 51 52 53 54 55 56 57 58 59 60
61 62 63 64 65

June 55th is an intercalary day that only occurs during leap years.

EpochEdit

To simplify the equation necessary to convert Gregorian dates to Martian dates, a common epoch is needed. Originally, the Gregorian epoch (January 1, 0001 CE) was used. However, it was later decided that the Davidian calendar would follow the same epoch as the Holocene calendar, with a minor adjustment to keep Martian seasons occuring during the same months as Earth seasons, as well as to ensure that Earth year 2000 is Martian year 6400.  This means that January 1, 0000 on the Davidian calendar is equivalent to January 1, 10037 BCE of the Gregorian calendar. This means that every date in recorded history is expressed in positive-numbered years.

Calendar dates use the suffix DM, to distinguish them from BCE/BC and CE/AD (Gregorian) and HE (Holocene). For dates that occurred before the epoch, negative numbers are used. For example, 20000 years before Year 0 would be expressed as -20000 DM.

Start of the year and SeasonsEdit

The solstices and equinoxes occur on the following dates:


Date Event (Northern Hemisphere) Event (Southern Hemisphere)
March 11 Spring Equinox Fall Equinox
June 34 Summer Solstice Winter Solstice
September 51 Fall Equinox Spring Equinox
December 29 Winter Solstice Summer Solstice

RationaleEdit

While other Martian calendars incorporate very creative things like new names for months, days of the week, etc, the Davidian Calendar builds from what is already familiar to future settlers. The term "sol" is not used. A "sol" is defined as the time between two successive noons or midnights. A "day" is more loosely defined as a period that roughly conforms to the human circadian cycle. Only on Earth and Mars are a "day" and a "sol" the same thing. On other planets, a "sol" is much longer or shorter than a "day". Therefore, the distinction is necessary and the term "day" is used in all Davidian calendars.

A 10-day week is used, rather than a 7-day week.  This is because a 10-day week makes more sense.  A week that is divided between 5 working days and 5 leisure or "weekend" days promotes a healthy life-work balance, and eliminates the need for holidays. Having half of the work force work the first half of the week and the other half working the second half of the week reduces the unemployment rate. The only reason why Earth calendars cling to a 7-day week is because of religious objections over the sabbath.  It is anticipated that Martian settlement will occur at a time when religion is no longer as dominant in advanced civilization.

ConversionEdit

The Davidian Calendar is unique among proposed Martian calendars in that it is designed to be converted back and forth between Davidian and Gregorian dates.

Gregorian to DavidianEdit

The formula for converting Gregorian (Earth) dates to Davidian (Martian) dates:

( (ED + 10037) * 365.26 ) / 686.98

  • Where "ED" = Earth Date

For example:

July 20, 1969 (1969.5479) is equivalent to October 21, 6383 (6383.7545).

( (1969.5479 + 10037) X 365.26) / 686.98 = 6383.7545

Davidian to GregorianEdit

The formula for converting Davidian (Martian) dates to Gregorian (Earth) dates:

( (MD X 686.98) / 365.26) - 10000

  • Where "MD" = Martian Date

For example:

December 2, 6365 (6365.9178) is equivalent to January 1, 1973 (1973.0006)

( (6365.9178 X 686.98) / 365.26) - 10000 = 1973.0006

Historical EventsEdit

Major world historical events, shown in Davidian, Gregorian, and Holocene dates. Note: approximate "circa" dates are rounded and do not calculate directly.

Events Davidian

(Mars)

Gregorian

(Earth)

Holocene

(Earth)

End of the Paleolithic Period,

All continents (except Antarctica) inhabited,
Agriculture and the domestication of animals begins.

c. 0 DM c. 10000 BCE c. 0 HE
Earliest walled city (Jericho) c. 530 DM c. 9000 BCE c. 1000 HE
First copper found in Middle East - beginning of Copper Age c. 2100 DM c. 6000 BCE c. 4000
Beginning of Indus Valley Civilization c. 3700 c. 3000 BCE c. 7000
Probable date of the completion of the first Egyptian pyramid 3928 2611 BCE 7390
Moses leads the Hebrews out of Egypt c. 4649 c. 1245 BCE c. 8748
Foundation of Rome 4917 753 BCE 9248
Imperial China, Qin dynasty 5199 221 BCE 9780
Birth of Jesus Christ 5314 5 BCE 9996
Possible year of Jesus' crucifixion 5332 30 CE 10030
Fall of Rome 5569 476 10476
Muslim conquests begin 5652 632 10632
Black Death decimates Asia and Europe 6030s 1340s 11340s
European discovery of the New World 6110 1492 11492
The United States of America declares independence from Britain June 18, 6261 July 4, 1776 July 4, 11776
French Revolution May 24, 6268 July 14, 1789 July 14, 11789
American Civil War 6306-6308 1861-1865 11861-11865
World War I 6334-6336 1914-1918 11914-11918
World War II 6348-6351 1939-1945 11939-11945
First human landing on the Moon January 55, 6364 July 20, 1969 July 20, 11969
Viking Landing on Mars October 7, 6367 June 19, 1976 June 19, 11976
Pathfinder Landing on Mars December 20, 6378 July 4, 1997 July 4, 11997
September 11 Terrorist Attacks March 6, 6381 September 11, 2001 September 11, 12001
Current Year 6386 2011 12011

HolidaysEdit

Holidays present a dilemma in a multi-planetary civilization. Holidays that celebrate significant historical events will probably be celebrated once per Martian year on the same date each year. Holidays of religious significance, such as Christmas, Easter, Passover, and Ramadan will probably be celebrated when they occur on Earth, regardless of what the date happens to be on Mars. This means they will occur twice annually in varying months and seasons.

Holiday Davidian

(Mars)

Gregorian

(Earth)

Ramadan 2010 Begins November 55, 6385 Begins August 11, 2010
Hanukkah 2010 January 53, 6386 December 2, 2010
Christmas 2010 February 20, 6386 December 25, 2010
Easter 2011 April 8, 6386* April 4, 2011
Ramadan 2011 Begins June 9, 6386 Begins August 1, 2011
Hanukkah 2011 August 37, 6386 December 21, 2011
Christmas 2011 August 41, 6386 December 25, 2011
Easter 2012 October 30, 6386* April 8, 2012
  • Easter on Mars presumably occurs on the Martian Sunday closest to the Earth Sunday it is observed on Earth, rather than on the actual calendar date.

External LinksEdit

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