Astrology is the forerunner of astronomy and its branch, cosmology. Essentially, astrology relates the movement of astronomical entities (sun, moon, planet, stars) with events on earth. For example, astrologers believe that the events that occur in individual lives are related to the movement of astronomical entities. They establish this relationship from charts called horoscopes, which map the movement of the astronomical entities at various times. The central framework for this mapping is the ecliptic: the plane that traces the orbits of the sun and the planets. The ecliptic is divided into twelve regions about 30º wide, called the zodiac (circle of animals). Excluding libra, all the constellations assigned to the regions were named after real or imaginary creatures: aries, taurus, gemini, cancer, leo, virgo, scorpio, sagittarius, capricorn, aquarius, and pisces. In ancient civilizations, the word constellation referred to the outlines of the “figures” humans imagined they saw in the stars of the night sky. However, in modern astronomy, constellation refers to both the group of stars and the particular region of the sky that contains them.
Astrologers assign signs to every planet including the sun and the moon according to the position of the planet on the ecliptic at the time the horoscope is charted. Each planet represents basic human drives and each sign represents a set of human traits. Also included in the horoscope are twelve divisions called houses, which account for the 24-hr period during which the earth rotates about its axis. Houses represent specific aspects of a person's life such as health and work. The predictions astrologers make are based on their interpretation of the position of astronomical bodies within the signs and houses of the horoscope. Astrology is practised by many people and its conceptual framework remains about the same as when it was first originated by the Sumerians, thousands of years ago before being used by the Chinese, Egyptian and Greek civilizations. So we see that ancient civilizations had knowledge of periodicity. Did they conceptualize it as time? If so, how did they define it? It is evident that time was not wholely conceptualized and abstractly defined by ancient humans. They were primarily concerned with developing utilitarian systems for the periodicity they observed in the environment in which they lived, particularly the periodic appearances of astronomical bodies such as the moon and the sun relative to earth's movement. A derivative of this focus is the calendar, a map that quantifies the experience of periodicity into groups of units (days, weeks, months, years).
The earliest formal calendar originated in ancient Babylonia. The Babylonians had a lunar calendar of twelve lunar months. A lunar month is the period between two full moons; or the number of days it takes the moon to circle the earth. Each lunar month contained thirty days. They added extra months when it was necessary to keep the calendar in agreement with the seasons of the year.
Ancient Egyptians established the calendar based on the solar year. A solar year is based on one revolution of the earth around the sun. They measured the solar year as 365 days, divided the days into twelve months of thirty days each, and appended five extra days. About 238B.C King Ptolemy III added an extra day every fourth year, an ancient version of the modern leap year.
About the same period, ancient Greece evolved its lunisolar calendar which had 354 days in a year. The ancient Greeks were the first to scientifically insert extra months at specific intervals in a cycle of solar years.
The calendar of ancient Rome was a variant of the Greek calendar. The year began in March (spring) and it had ten months made up of 304 days. Later, about the 7th centuryB.C., the months January and February were added. An extra month had to be inserted approximately every second year because the months were 29 or 30 days long. The arithmetic for designating the days was awkward. Days were designated by counting backwards from three pegged numbers: the calends (first of the month); the ides (middle of the month which fell on the 13th day for some months and on the 15th for others); and the nones (the 9th day before the ides). This technique was cumbersome and often politically manipulated.
In 45 B.C., the Roman ruler Julius Caesar introduced an improved calendar based on a purely solar year. This calendar was called the Julian Calendar. It fixed the normal year at 365 days and the leap year, every fourth year, at 366 days. The Julian Calendar also established the order of the months and the days of the week as they exist in modern western calendars. Julius Caesar renamed the month Quintilis; Julius (July), after himself. Later, the month Sextilis, was renamed Augustus (August), after Emperor Augustus. The Julian Calendar was not quite accurate. It was about 11 minutes and 14 seconds longer than the solar year. These extra minutes and seconds accumulated into days over the years and in 1582 A.D., the vernal equinox occurred 10 days early. As a result church holidays did not occur in the appropriate seasons. Pope Gregory XIII, displeased with the discrepancy between the vernal equinox and March 21, decreed that 10 days be dropped from the calendar so that the vernal equinox can occur on March 21 as it did in 325 A.D., the date of the First Council of Nicaea. In ordr to prevent future inaccuracies, he instituted the Gregorian Calendar. The Gregorian calendar required that century years that are multiples of 400 (i.e. divisible by 400 without a remainder) be leap years and all other century years be common years. The Gregorian Calendar was eventually adopted throughout Europe. In 1752 A.D., Britain made two adjustments: it corrected the 11-day discrepancy by changing the day after September 2, to September 14. It also adopted January 1 as the beginning of a new year. The Gregorian Calendar is used today in most parts of the world.
Peter Oye Sagay