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.
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 7 days, same as on Earth.
Month: A unit of time that on Mars simply means 1/12 of a year.
Year length and intercalation
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.
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.
The year is divided into 12 months. All months except for June and October have 56 days. February has 55 days during common years and 56 days during leap years. June and October have 55 days.
The days of the week are the same as the Gregorian calendar, with the exception of Tuesday, which has been replaced with Gaiaday. This is because Tuesday is named after Mars and it would be more appropriate to replace it on the Martian calendar with a day that is named after Earth.
- February 56th is an intercalary day that only occurs during leap years.
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. This means that January 1, 0000 on the Davidian calendar is equivalent to January 1, 10001 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 Seasons
Because the Davidian epoch is based on a common January 1st between the Davidian and Holocene calendars, the beginning of the year is completely unrelated to seasons. In fact, Martian seasons begin in months that would be strange on Earth:
|Date||Event (Northern Hemisphere)||Event (Southern Hemisphere)|
|January 35||Fall Equinox||Spring Equinox|
|April 10||Winter Solstice||Summer Solstice|
|June 51||Spring Equinox||Fall Equinox|
|October 22||Summer Solstice||Winter Solstice|
While other Martian calendars (notably the Darian calendar) 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 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 Davidian
The formula for converting Gregorian (Earth) dates to Davidian (Martian) dates:
( (ED + 10000) * 365.26) / 686.98
- Where "ED" = Earth Date
July 20, 1969 (1969.5479) is equivalent to January 55, 6364 (6364.0820).
( (1969.5479 + 10000) X 365.26) / 686.98 = 6364.0820
Davidian to Gregorian
The formula for converting Davidian (Martian) dates to Gregorian (Earth) dates:
( (MD X 686.98) / 365.26) - 10000
- Where "MD" = Martian Date
December 2, 6365 (6365.9178) is equivalent to January 1, 1973 (1973.0006)
( (6365.9178 X 686.98) / 365.26) - 10000 = 1973.0006
Major world historical events, shown in Davidian, Gregorian, and Holocene dates. Note: approximate "circa" dates are rounded and do not calculate directly.
|End of the Paleolithic Period,
All continents (except Antarctica) inhabited,
|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|
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.
|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.
- http://akdave.wikia.com/wiki/Davidian_Martian_Calendar The Davidian Martian Calendar at the AKDave Wiki