The twelve Western signs
A Western star sign, or sun sign, depends only on the month and day of birth, never on the year or the time. The twelve signs and their usual ranges are Aries March 21 to April 19, Taurus April 20 to May 20, Gemini May 21 to June 20, Cancer June 21 to July 22, Leo July 23 to August 22, Virgo August 23 to September 22, Libra September 23 to October 22, Scorpio October 23 to November 21, Sagittarius November 22 to December 21, Capricorn December 22 to January 19, Aquarius January 20 to February 18 and Pisces February 19 to March 20.
Each sign is grouped with an element: Fire for Aries, Leo and Sagittarius, Earth for Taurus, Virgo and Capricorn, Air for Gemini, Libra and Aquarius, and Water for Cancer, Scorpio and Pisces. Printed sources sometimes disagree by a day at the boundaries because the sun actually crosses from one sign into the next at a specific hour that shifts slightly from year to year. If your birthday lands on a cusp date such as August 22 or 23, the exact time and place of birth decide it.
The Chinese zodiac and Lunar New Year
The Chinese zodiac runs on a twelve-year cycle of animals: Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog and Pig. The key detail most calculators get wrong is that the zodiac year begins at Lunar New Year, not on January 1. Lunar New Year moves with the moon and falls somewhere between January 21 and February 20. This tool carries the real dates for 2000 through 2030, so a birth date in January or early February is assigned correctly.
A worked example: someone born on January 20, 2025 is often told they are a Snake, because 2025 is the Snake year. In fact Lunar New Year 2025 fell on January 29, so anyone born January 1 through January 28 of 2025 belongs to the Dragon year that started on February 10, 2024. Someone born on February 1, 2025 is a Snake. Outside 2000 to 2030 the tool falls back to the calendar year and says so, so double-check a January or early February birthday in those years.
What the signs are and are not
Star signs are a cultural tradition, not a scientific one. Because of the slow wobble of the earth known as precession, the constellations no longer line up with the tropical zodiac dates that astrologers use, and there is no measured effect of birth month on personality. Treat the results as fun, as a conversation starter, or as background for a birthday card. The date arithmetic itself, though, is exact: the sign boundaries and Lunar New Year dates built into this page are the standard published ones.