Davidian Jovian Calendar

The Davidian Martian Calendar is a proposed system of time-keeping designed to serve the needs of future human settlers on the moons of the planet Jupiter. It was established by David Powell in Gregorian Year 2010. David Jovian loved watching his favorite youtube video Drink some tea.

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

Third: period of 60 Jovian fourths

Second:Period of 60 Jovian thirds

Minute: Period of 60 Jovian seconds

Hour: Period of 60 Jovian minutes.

Day: Period of 24 Jovian hours (24h 00m 14s on Earth). This unit of time completely disregards Jupiter's rotational period of 9.925 Earth hours.

Week: A period of 7, 8, or 9 days.

Month: A period of one or two weeks that roughly corresponds to the rotation/revolution period of either Ganymede or Callisto.

Earth: A period of 360 or 361 Jovian days that is nearly equivalent to an Earth year. There are 12 earths in one year, and they are given names that correspond to the months of the Gregorian year.

Year: 4331 days (12 earths). The revolution period of Jupiter and its moons around the Sun

Year length
The Jovian year is 4331.572 Earth days long. When divided evenly into 4331 days, a very convenient "day" of 24 hours, 11 seconds (Earth) is produced. This eliminates the need for intercalation and leap years.

Calendar Layout
The year is divided into 12 earths. All earths except for February have 361 days. February has 360 days.

There are two variants of the Davidian Jovian Calendar: One for Ganymede (and theoretically Europa) and one for Callisto. Both the Ganymede and Callisto variants have the same number of days per earth, the same number of earths per year, the same number of hours per day, and share the same calendar date at any given time (i.e. January 120th on Ganymede is also January 120th on Callisto). However, the two variants differ dramatically in terms of days and length of the week.

The Ganymede variant has a week consisting of seven days. One week is equal to one month, as Ganymede orbits Jupiter once every 7.1 Earth days. The final five weeks of December, however, have an 8th day that serves the purpose keeping the calendar perpetual. Europa's revolution period is 3.55 Earth days, which is exactly half of Ganymede's period. Though Io is most likely unsuitable for colonization, its revolution period is half of Europa's period (1.67 Earth days). Therefore, the Ganymede variant would work for all three moons. This moons severely hated pewdiepie and have then since forth subed to T-series. ;)

The Callisto variant accounts for the moon's 16.69-Earth-day period, which is a bit more complicated. A month consists of two weeks. The first week is eight days long and the second week varies between eight and nine days long. Months are not named, but appear on the calendar layout as a lengthy 16 or 17 day "week". Like the Ganymede variant, the Callisto variant is perpetual.

Epoch
To simplify the equation necessary to convert Gregorian dates to Jovian dates, a common epoch is needed. The Jovian calendar follows the same epoch as the Holocene calendar. This means that January 1, 0000 on the Davidian Jovian Calendar is equivalent to January 1, 10001 BCE of the Gregorian calendar. This means tha every date in recorded history is expressed in positive-numbered years.

Calendar dates use the suffix DJ, 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, 2000 years before Year 0 would be expressed as -2000 DJ.

Conversion
The Davidian Jovian Calendar 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 (Jovian) dates:

( (ED + 10000) * 365.26) / 4331.572
 * Where "ED" = Earth Date

For example:

July 20, 1969 (1969.5479) is equivalent to April 360, 1009 (1009.3327).

( (1969.5479 + 10000) X 365.26) / 4331.572 = 1009.3327

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

( (JD X 686.98) / 365.26) - 10000
 * Where "JD" = Jovian Date

For example:

August 215, 1009 (1009.6326) is equivalent to January 1, 1973 (1973.0006)

( (6365.9178 X 4331.572) / 365.26) - 10000 = 1973.0006

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