Astronomy

Êuê Calendar: The Solar Calendar – The Sun and the Constellations of the Zodiac

The Earth in its orbit around the Sun causes the Sun to appear on the celestial sphere moving along the ecliptic (red), which is tilted 23.44° with respect to the celestial equator (blue-white). The constellations of the Zodiac are in green. Image credit: Wikipedia.

Shalom everyone! Genesis 1:14-16 gives the account of Day 4 of the Creation in which Elohim divided the day from the night. He created two great lights, one with greater power than the other: The greater light, also known as the Sun, He created to rule the day; the lesser light, also known as the Moon, He created to rule the night. Elohim also created the stars to be used in conjunction with the Sun and Moon to assess the seasons, days and years.

The ancient pre-exilic Israelites used two calendar systems to keep time due to the two turns of the year, Spring and Fall: An ecclesiastical lunar calendar to track the mo’edim and the reigns of kings, with its year beginning in the Spring; and a civil solar calendar for day-to-day secular business with its year beginning in the Fall. The ecclesiastical lunar calendar utilized the phases of the Moon to track time during a lunar month. Each full moon marked the beginning of a new month, each month being about 29.5 days. Each lunar year had 12 or 13 full moons. The civil solar calendar utilized the positions of the Sun and the stars relative to the Earth’s rotation and annual orbit.  Each year on the solar calendar consisted approximately 365 days. The first sighting of the Sun in each of the constellations visible to the naked eye during ancient times marked the beginning of a new month on the solar calendar. There were 12 months in each year, and each month had either 29, 30 or 31 days.

While the solar calendar was the for civil affairs, the last day of the weekly cycle  was always a Sabbath, a day of rest. While lunar calendar tracked the mo’edim due to their reliance upon the Moon, the Sabbath/Shabbat was independent of the ecclesiastical lunar calendar and was tracked according to the civil solar calendar. The civil solar calendar and ecclesiastical lunar calendar complemented each other in the ancient Israelite culture.


The Sun

The Sun is at the center of our Solar System. It is made of hot plasma and is the most important physical source of energy for life on planet Earth. It is a stationary object that is orbited by a number of other objects including: Eight known planets – four terrestrial planets (Mercury, Venus, Earth and Mars), two gas planets (Jupiter and Saturn), two ice planets (Uranus and Neptune); five known dwarf planets (Pluto, Ceres, Eris, Makemake and Haumea); asteroids, comets and other icy objects. Our Solar System also has groups of stars called “constellations.” Like the Sun, the constellations are stationary but they appear to “move” in the night sky due to the Earth‘s rotation and annual orbit around the Sun. The Moon , the lesser light Elohim created to rule the night, orbits the Earth.

In astronomy, all objects in our Solar System form the “celestial sphere,” an imaginary sphere of which the observer is the center and on which all celestial objects are considered to lie. Like planet Earth, this celestial sphere has assigned axes (north celestial pole and south celestial pole), coordinates for measuring the positions of celestial objects in the sky (sun, planets, stars , constellations etc) and a celestial equator. The circular “orbit” the Sun appears to follow on the celestial sphere over the course of one year is called the “ecliptic.” According the scientific research, one year of this solar orbit consists of 365.2425 days. The celestial sphere also has a celestial equator, an imaginary line on the same plane as the Earth‘s equator. Because the Earth‘s axis is tilted, the celestial equator is inclined at 23.44 degrees relative to the ecliptic plane.

The Sun and the Seasons: Equinoxes and Solstices

The Sun is key in the determination of the arrival of the four seasons, Spring, Summer, Fall and Winter. Spring and Fall begin with the arrival of the Equinoxes. Summer and Winter begin with the arrival of the Solstices.

The Equinox is the time when the Sun crosses the plane of the Earth‘s equator, making night and day of approximately equal length all over the Earth. The Vernal (Spring) Equinox occurs about March 19, 20 or 21 in the Northern Hemisphere, and approximately September 22 in the Southern Hemisphere. The Autumn (Fall) Equinox occurs approximately September 22 in the Northern Hemisphere, and about March 19, 20 or 21 in the Southern Hemisphere.

The Solstice is the time when the Sun appears to reach its most northerly or southerly point in the sky at noon, and are marked by the longest and shortest days of the year. The Summer Solstice occurs annually around June 21 when the Sun is at its most northerly point from the Earth‘s equator and is the longest day of the year. The Winter Solstice occurs annually around December 21, when the Sun is at its most southerly point relative to the Earth‘s equator, and is the shortest day of the year.


The Stars: The Constellations of the Zodiac

A visual representation of the Earth’s orbit in relation to the Sun and the constellations, and the calendar months. Image credit: Unknown

Constellations are groups of stars that form meaningful patterns in the celestial sphere. These patterns typically represent animals, mythical beings or creatures, or inanimate objects. The International Astronomical Union (IAU) confirms that there are 88 constellations  covering the entire celestial sphere. In ancient times, only 48 constellations were known to astronomers.

About 8-degrees north and south of the ecliptic lies an area of the sky called the Zodiac, a circle of twelve 30-degree divisions of celestial longitude that are centered on the ecliptic. Within the Zodiac lie 13 constellations of stars which are visible to the naked eye from Earth. Though the International Astronomical Union (IAU) confirmed 13 constellations in the Zodiac in 1995, the ancient Mesopotamian and Egyptian astronomers referred to 12, and used the start date of the Sun‘s position in each of these constellations as the instance of a new month on the 365-day solar calendar.

Sidereal Solar Year and Constellations

Ancient Mesopotamian astronomers used the sidereal system to define a solar year. The sidereal system reckons the Earth‘s position in relation to the fixed positions of the stars in the celestial sphere. The dates when the Sun appeared nearest to a constellation were used to reckon a month. The ancient sidereal system originally divided the Zodiac into 12 constellations. The modern sidereal system divides the Zodiac into 13 constellations. The ancient Egyptian astronomers used the sidereal system up until the time of Ptolemy, who introduced the tropical system to define a solar year, based on the Earth‘s position relative to the Vernal Equinox in the Northern Hemisphere. The ancient pre-exilic Israelites used the ancient sidereal system to reckon time for their civil solar calendar, which began the year in the Fall with the Virgo constellation. The sidereal system is used today primarily by Eastern astronomers.

The following are the constellations of the Zodiac and their dates when the Sun “passes” through them according to the sidereal system. The names of these constellations are English translations, naturally each culture would have given the constellations names in their own language.

# Constellation Symbol Sidereal Dates # Days IAU Sidereal Dates # Days
1  Pisces Fishes  Mar 16 – Apr 14 31  Mar 11 – Apr 18 38
2  Aries Ram  Apr 15 – May 15 31  Apr 18 – May 13 25
3  Taurus Bull  May 16 – Jun 15 31  May 13 – Jun 21 39
4  Gemini Twins  Jun 16 – Jul 16 31  Jun 21 – Jul 20 29
5  Cancer Crab  Jul 17 – Aug 16 31  Jul 20 – Aug 10 21
6  Leo Lion  Aug 17 – Sep 16 31  Aug 10 – Sep 16 37
7  Virgo Maiden holding wheat stalks  Sep 17 – Oct 17 30  Sep 16 – Oct 30 44
8  Libra Scales/Weights  Oct 18 – Nov 16 30  Oct 30 – Nov 23 24
9  Scorpio Scorpion  Nov 17 – Dec 16 30  Nov 23 – Nov 29 6
10  Ophiuchus Snake  N/A  Nov 29 – Dec 17 18
11  Sagittarius Archer  Dec 17 – Jan 15 30  Dec 17 – Jan 21 35
12  Capricorn Goat-Fish  Jan 16 – Feb 14 29  Jan 21 – Feb 16 26
13  Aquarius Water-Bearer  Feb 15 – Mar 15 30  Feb 16 – Mar 11 23
 Total: 365  Total:  365

Tropical Solar Year and Constellations

The tropical system is used primarily by Western astronomers, though use of the sidereal system among them is gaining traction. The tropical system divides the Zodiac into 12 constellations. Today, the Ga-Dangmes of Ghana, descendants of the Israelite tribes of Gad and Dan, use the tropical system as the basis for their solar calendar. It should be noted that the Ga-Dangmes spent many years in ancient Egypt after their exile from Israel; in Egypt they would have been introduced to the tropical system developed by Ptolemy.

The following are the constellations of the Zodiac and their dates when the Sun “passes” through them according to tropical system. The names of these constellations are English translations, naturally each culture would have given the constellations names in their own language.

# Constellation Symbol Tropical Dates # Days
1  Aries  Ram  March 21 – April 20  31
2  Taurus  Bull  April 21 – May 21  31
3  Gemini  Twins  May 22 – June 21  31
4  Cancer  Crab  June 22 – July 22  31
5  Leo  Lion  July 23 – August 22  31
6  Virgo  Maiden holding wheat stalks  August 23 – September 22  31
7  Libra  Scales/Weights  September 23 – October 22  30
8  Scorpio  Scorpion  October 23 – November 21  30
9  Sagittarius  Archer  November 22 – December 21  30
10  Capricorn  Goat-Fish  December 22 – January 19  29
11  Aquarius  Water-Bearer  January 20 – February 19  31
12  Pisces  Fishes  February 20 – March 20  29
 Total Number of Days:  365

The Gezer Calendar – Practical Application of the Civil Solar Calendar

The Gezer calendar inscribed in Proto-Canaanite or Paleo-Hebrew. Image credit: Wikipedia

The Gezer calendar gives some insight into how the ancient Canaanites and Israelites structured their year based upon the civil solar calendar. Found in 1908 by Irish archaeologist R.A. Stewart Macalister in the ancient Canaanite city of Gezer, 20 miles west of Jerusalem, the Gezer calendar is a small limestone tablet inscribed in either the Proto-Canaanite or Paleo-Hebrew language. Archaeologists date the calendar back to 10th century BCE. The calendar is currently being housed in the Istanbul Archaeology Museums.

The inscription on the Gezer calendar describes the duties to be carried out in each month or bi-monthly such as planting, sowing, harvesting and maintaining crops. The words are written like a rhyme, which has led scholars to believe that the inscription was either a memory exercise or rhyming exercise for children. The following is a translation of the Gezer calendar inscription in English:

“Two months gathering,
Two months planting,
Two months late sowing,
One month cutting flax,
One month reaping barley,
One month reaping and measuring grain,
Two months pruning,
One month summer fruit

Abiyah”

Based upon the inscription above, we see that the civil solar calendar began in the Fall (Virgo, First Month) and ended in the following Summer (Leo, Twelfth Month). The year number increments by one in the Fall. Using the original sidereal system known to the region during ancient times, the following is an example of how the civil year would have looked for the ancient pre-exilic Israelites:

Month # Gezer Calendar Inscription Crop Season Constellation Sidereal Dates
1 Two months gathering Fruits: Grapes, figs, datespomegranates and olives Fall Virgo Sep 17 – Oct 17
2 Fall Libra Oct 18 – Nov 16
3 Two months planting Grains: Wheat, barley, oats, etc. Fall Scorpio-Ophiuchus Nov 17 – Dec 16
4 Winter Sagittarius Dec 17 – Jan 15
5 Two months late sowing Grains: Wheat, barley, oats, etc. Winter Capricorn Jan 16 – Feb 14
6 Winter Aquarius Feb 15 – Mar 15
7 One month cutting flax Grains: Flax Spring Pisces Mar 16 – Apr 14
8 One month reaping barley Grains: Barley  Spring Aries Apr 15 – May 15
9 One month reaping and measuring grain Grains: Wheat, oats, etc.  Spring Taurus May 16 – Jun 15
10 Two months pruning Fruits: Fruit trees, vines etc. Summer Gemini Jun 16 – Jul 16
11 Summer Cancer Jul 17 – Aug 16
12 One month summer fruit Grapes, figs, datespomegranates and olives Summer Leo Aug 17 – Sep 16

From the above translation and table, we can see that the civil solar year began in the Fall with the constellation of Virgo. The first and second months of the civil year, Virgo and Libra, were devoted to the final gathering of the Fall harvest of the fruit usually grapes, figs, datespomegranates and olives. The third and fourth months, ScorpioOphiuchus and Sagittarius respectively, were devoted to planting grains such wheat, barley, and oats in the late Fall to early Winter for harvest in the Spring. The fifth and six months, Capricorn and Aquarius respectively, were devoted to continued sowing of grain in mid-to-late Winter. The seventh month, the early Spring, was devoted to the cutting of the flax harvest. Barley was harvested in the Spring in the eighth month, Aries, in mid-Spring. Wheat was harvested in the ninth month, Taurus, in the late Spring. The tenth and eleventh months, Gemini and Cancer, were devoted to the pruning of fruit trees in the early to mid-Summer. The twelfth and last month of the civil solar year, Leo, was devoted to harvesting fruit in the late Summer, typically grapes, figs, dates, pomegranates and olives.

The civil solar calendar was therefore extremely important to ancient pre-exilic Israelite agriculture, food security, business dealings and economic performance.  If you use Google Calendar, please follow our public calendars Sidereal Solar Calendar or “Tropical Solar Calendar” for a civil solar calendar synchronized to the Gregorian calendar. All times are based in the east coast USA time zone.

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