I wanted to ignore this because it is not new, and not news. Enough people have asked that it is time to weigh in. I REALLY wanted to ignore this.
Astrology is Not Science
Keep your sign. Change your sign. It’s your decision, not science.
I expect voicing this opinion and linking to this article  will get me dismissed as lunatic and a scab by all the other astronomers out there, but I’d like to point out I am NOT supporting astrology. I agree with paragraphs 1-5 of the linked article, and ignore paragraphs 6-10 as the usual non-science stuff to which I can’t give merit. This is the key section:
“Back to basics. Astrology works off a mathematically exact zodiac marked out from Zero Point Aries which is a line through the centre of the earth. That zodiac circle divided into twelve equal segments is named after twelve of the eighty eight constellations in the heavens which are roughly in a circle.
“If you think of the astrological zodiac as a map grid reference it helps. Constellations vary enormously in size and distance from the earth so would hardly be useful for accurate predictions.”
Astronomy is the science that sprang from the belief system of astrology many, many years ago. Since that time, astrology and astronomy have evolved along separate tracks. Current astronomy has no bearing on current astrology and vice versa, though they share a common ancestor. Just like I’m not going to tell you not to believe in whichever god you prefer, I’m not going to tell you not to believe astrology. I’m just going to say it isn’t science. Neither is the god thing.
So, if you want to know which sign will predict your personality, I can’t help you. That’s their territory, and they’ll say the same sign they’ve always said. You can keep your “sign.”
If you want to know which constellation the Sun is in on the day of your birth, that I can tell you, and it likely is off by about one from the one astrologers give you. It will have no bearing on your personality though.
In short you can keep your sign or change it. You can pick a different constellation entirely if you want. This is a personal decision, with no scientific merit any way you do it.
Some Good Articles
Why are we talking about this now? It seems to have gone viral. Like I said, not news, but an article hit the internet at the right time in the right place, just like rick-rolling and every other meme ever, and now everyone is talking.
Bad Astronomy – Astrological Sign of the Times 
Cosmic Log 
Thanks to my friend R.T. for sending me the astrology.com link.
~ A l i c e !