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Length of time unit:  91-92 days

Historical use of Quarters in solar calendars

Many historical  calendars have divided the year in to both quarters and months. One of the solar calendars developed in China prior to the Eastern Zhou dynasty (which began in 771 BCE) had this structure.  In 1887, 1900, and 1930 CE, reforms were proposed to the Gregorian Calendar that would divide the year into four quarters of 91 days each, and then each quarter would be subdivided by two months with 30 days and one month with 31 days. The four quarters would total 364 days, and this was proposed because 91 days (and 364) equally divides into 13 weeks of 7 days each. This would allow the quarters to start on the exact same day of the week.  The 365th and, if necessary, 366th day would not be assigned to a day of the week. This would have created a perennial calendar where the same month and day layout could be re-used every year.

The 1930 proposal, known as the World Calendar,  gradually grew in popularity to the point that it was introduced as legislation in the United States Congress and proposed before the United Nations in 1955. However, the United States blocked it with a provision that would require the U.S. Congress to adopt it in order to support the world resolution.

In 1973, science fiction writer and essayist Isaac Asimov proposed the  World Seasons Calendar which was similarly structured to the World Calendar, but eliminated the subdivisions of months within quarters, which he named A, B, C, and D. (Asimov, I. (1973). The Tragedy of the Moon. United Kingdom: Doubleday).

The objections to such calendar reforms has been that Judaism, Christianity and Islam require a Sabbath to be observed every seven days, and that such days would involve breaks from work.  While one of the first people to propose a “leap day” outside of the week was, in fact, an Italian priest named Marco Mastrofini, other people from these Abrahamic religions have objected. Having an additional day added each year would create an eight-day gap between sabbaths once per year. Some interpretations of the Sabbath requirement would force each of these religions to change their holy days every year, which is not practical when the modern work world is so closely tied to the seven-day week.

Rationale and practicalities using quarters

A thirteen-week Quarter makes it easier to use the calendar to plan weeks ahead of time without having to turn the calendar page. Have you ever turned a calendar page to the next month only to be surprised by a major deadline early in the month?  This becomes less likely with the ability to see thirteen weeks all at once on the page.

Another practical reason for using Quarters is that it becomes easier for someone less familiar with the Earth Epic Calendar to figure what part of the year they are in, as the calendar is tied to the periods of time between equinoxes and solstices–which serve as the seasons in most calendars.  Early in the Quarter means early in the season and later in the quarter means later in the season.

Local cultures should name the Quarters in this calendar however they wish.  I spoke before as to how the worldwide adoption of the Gregorian calendar is a reflection of cultural imperialism.  Letting local cultures name the quarters would be a way to let them reclaim the calendar while still providing accuracy and uniformity of standards worldwide.

Even though local cultures should determine the name of the quarters as they deem appropriate, a worldwide standard is needed so that different cultures would have a common frame of reference.  This worldwide standard shouldn’t rely on the names of the seasons themselves, as Spring in the Northern Hemisphere is the same as Autumn in the Southern Hemisphere, and the four seasons designation is irrelevant in many parts of the world.  Isaac Asimov’s World Season Calendar proposed transcending this by using the first four letters of the alphabet. But it would be better to have something more descriptive, so that the quarter is easy to identify and to reflect the  dramatic and magical nature of the change in seasons as it exists in many parts of the world.

At the December Solstice, the sun reaches its most southern point at the Tropic of Capricorn, and on the June Solstice the sun reaches its most northern point at the Tropic of Cancer.  (That’s how these tropical lines got their names–they correspond to the astrological assigned associated with that time of year).  The December Solstice and the quarter following it is thus referred to as Southlight and the June Solstice and the quarter following it is referred to as Northlight.

What about the remaining quarters?  From the rotating Earth’s standpoint, the sun moves from east to west.  As such, the second quarter–the one following the Northward Equinox (Spring in the North, Autumn in the South) is referred to as Eastlight.  The Quarter following the Southward Equinox (Autumn in the North, Spring in the South) is then referred to as Westlight.  If the sun moves from East to West through the day, why shouldn’t it move the same “direction” through the year as well?

Quarters versus actual seasons

One fact that is not well known is that while the Quarters on the Earth Epic Calendar are about the same, the actual length of the seasons is not.  Due to the elliptical nature of the earth’s rotation, the lengths of the astronomical seasons vary from lengths of the Quarters described in this calendar—astronomical spring, summer, fall and winter currently vary in length between 88-93 days.

In planning the calendar, the decision was made to lean towards quarters of equal length because it would be easier for planning. Currently, the Northern Hemisphere winter lasts 88.99 days, spring lasts 92.75 days, summer lasts 93.65 days, and autumn lasts 89.85 days. As such, the length of time between the March and September equinoxes is 7.56 days longer than from between the September and March equinoxes.  With the Gregorian Calendar, we have a hard enough time remembering which months have 31 days and which have 30 days–imagine having four different quarters of varying lengths.

The Solar Hijri calendar accounts for this by having all of the months between the Spring and Fall Equinoxes contain 31 days, whereas all of the months between the fall and Spring Equinoxes, all of the months have 30 days, or in the case of the last one, 29 days. This difference of 6 or 7 days parallels the lengths of the seasons closely.  Because the Earth Epic Calendar puts simplicity over accuracy in this particular case, the Solar Hijri calendar will be more accurate that the Earth Epic Calendar.

But with equal length quarters, the Earth Epic Calendar still has to figure out what to with the 365th day and the 366th day.  As such, the Earth Epic Calendar put the 365th day in the quarter corresponding to the longest season of the year, and the 366th day in the second longest season of the year.  As it currently stands, summer is the longest season and spring is the second longest season of the year so the 365th day and 366th day are assigned to Northlight and Eastlight respectively.

Axial precession and leap days
Impact of Earth’s axial precession and elliptical orbit on the lengths of seasons. Image By Cmglee – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=30359851

But notice in the diagram on the right that the lengths of the seasons change.  This is because of the elliptical nature of Earth’s orbit around the sun.  It takes more days to go between the Spring Equinox and the Fall Equinox than the reverse because it takes more days to travel through the long part of the ellipse that is Earth’s orbit.  Earth is physically closest to the sun on January 3 and furthest from the sun on July 4. But in 5,000 years, around 16700 EE, Autumn will be the longest, followed by Northlight, so Westilght and Northlight will be the respective recipients of the extra days.  And in another 5,000 years, around 21700 EE, Winter will be the longest, followed by Westlight, so Southlight and Westlight will be the recipients respectively.

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