As it seems, the star doctors decided that the Babylonian horoscope created 3000 years ago is outdated, so they added a 13th sign called Ophiuchus. There is also a whole shift in the dates from other signs, so you might want to check them out, to be able to base your personality on those magazine articles properly.
Here is the new list:
Capricorn: Jan. 20 - Feb. 16
Aquarius: Feb. 16 - March 11
Pisces: March 11- April 18
Aries: April 18- May 13
Taurus: May 13- June 21
Gemini: June 21- July 20
Cancer: July 20- Aug. 10
Leo: Aug. 10- Sept. 16
Virgo: Sept. 16- Oct. 30
Libra: Oct. 30- Nov. 23
Scorpio: Nov. 23- Nov. 29
Ophiuchus: Nov. 29- Dec. 17
Sagittarius: Dec. 17- Jan. 20