The ancient Babylonians based zodiac signs on the constellation the sun was "in" on the day a person was born. During the ensuing millenniums, the moon's gravitational pull has made the Earth "wobble" around its axis, creating about a one-month bump in the stars' alignment...
Indeed, most horoscope readers who consider themselves Pisces are actually Aquarians. So instead of being sensitive, humane and idealistic, they actually are friendly, loyal and inventive. Or not.
At the link, the following new alignments are offered:
Astrology buffs should be using these dates, reflecting where the stars currently are aligned: 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. 23-29. Ophiuchus:* Nov. 29-Dec. 17. Sagittarius: Dec. 17-Jan. 20.
* Discarded by the Babylonians because they wanted 12 signs per year.