The birth dates of the 12 zodiac signs start between the 18th and 23rd day of each month. The dates are not exact because the sun moves through the signs on different dates each year, states About.com.
Give or take a day or two, the birth dates for each sign are March 20 to April 20 for Aries, April 20 to May 21 for Taurus, May 21 to June 21 for Gemini, June 20 to July 21 for Cancer, July 22 to August 23 for Leo, August 23 to September 23 for Virgo, September 23 to October 23 for Libra, October 22 to November 22 for Scorpio, November 22 to December 22 for Sagittarius, December 22 to January 20 for Capricorn, January 20 to February 18 for Aquarius and February 18 to March 20 for Pisces.
Anyone born near the beginning or end of a sign is considered on the cusp, with characteristics of both signs, according to About.com.
People have used astrology for centuries to predict human behavior. The 12 signs of the zodiac were created by the ancient Babylonians more than 3,000 years ago. Astrology, which is a belief system, is sometimes confused with astronomy, which is the scientific study of outer space. There is no evidence that astrology actually works, as NASA notes.