Astronomy is formally defined by the Oxford Dictionary as the branch of science which deals with celestial objects, space, and the physical universe as a whole.
Astrology, although very similar to astronomy,  is arguably more complex and objective. Astrology is the study of the movements and relative positions of celestial bodies interpreted as having an influence on human affairs and the natural world.
One of the very first concepts of astrology, the 12 zodiac signs, were created by the Babylonians in 1894 BC. The Babylonians lived in Babylon, one of the most famous ancient Mesopotamian cities, which is roughly where modern-day Iraq is. 
Hammurabi, the sixth king of the First Babylonian Dynasty, established “the Hammurabi code of laws, a collection of 282 rules, established standards for commercial interactions and set fines and punishments to meet the requirements of justice,” according to Ancient History Encyclopedia. Hammurabi established the very first law code in history in order to create a just system for lawmaking in society.
“The Babylonians were known to have mapped out the fixed stars and various constellations,” Emma Wilson from Kepler College said, “Names were given to the constellations and prior to specific zodiac signs’ the seeming planetary movement through each constellation appeared to hold significance.”
The Babylonians followed a 12-month calendar, so they assigned each month a zodiac sign. 
According to earthsky.com, “Over the course of a year, the sun appears to be in front of, or ‘in’, different constellations, one month, the sun appears in Gemini; the next month, in Cancer. The dates listed in the newspaper’s horoscope identify when the sun appears in a particular astrological sign.”
The modern zodiac signs are a direct result of the beliefs and observations of the Babylonians, who lived over 4,000 years ago, which goes to show the role that zodiac signs have had in world history. 
Below is a list of the zodiac signs, and the dates that correspond with each sign. Something important to note, however, is that if someone is born on the “cusp” of two zodiac signs, they can identify with multiple traits from different signs. For example, if someone is born on April 19, they may find that they have some Aries traits and some Taurus traits because their birthday lies on the border of the zodiac signs. 

Aries (March 21-April 19)
Taurus (April 20-May 20)
Gemini (May 21-June 20)
Cancer (June 21-July 22)
Leo (July 23-Aug. 22)
Virgo (Aug. 23-Sept. 22)
Libra (Sept. 23-Oct. 22)
Scorpio (Oct. 23-Nov. 21)
Sagittarius (Nov. 22-Dec. 21)
Capricorn (Dec. 22-Jan. 19)
 Aquarius (Jan. 20 to Feb. 18)
Pisces (Feb. 19 to March 20)