Here's why:

* Zodiac signs are based on the position of the sun at the time of your birth. This position is fixed and doesn't shift.

* Astrology uses the tropical zodiac, which is based on the Earth's position in relation to the sun. This system defines specific dates for each sign.

However, there are a few things that might lead to confusion:

* The cusp: If you were born very close to the boundary of two signs, you might feel like you share characteristics of both. This is called being on the cusp.

* Misunderstanding of the concept: Some people mistakenly believe that your astrological sign can change based on other factors like your personality or experiences.

* Misinformation: There are some websites and publications that promote inaccurate information about astrological signs.

In summary: Your astrological sign is determined by the position of the sun at your birth and doesn't change throughout your life. If you're unsure of your sign, you can use a reliable online birth chart calculator or consult an astrologer.