Let's take that back a tack... how old is astrology supposed to be?
And what kind of calender did we have then?
There's a reason why it's month, and that reason is lunar. Lunar calendars have 13 months. Ring a bell?
It affects Eastern astrology, which uses a different method of figuring out signs and horoscopes. For example, the difference between the Chinese form of astrology and ours. We don't have things like the Year of the Boar, or the Ox, or the Pig, etc., and they're on a lunar calendar, to boot, IIRC.
For Western astrology, it's like someone announcing a monumental change to the Greek alphabet...to a bunch of English speakers. Interesting, but doesn't figure into how they spell anything.
Enjoy your morning horoscope in the paper with a clear conscience!
Mittens are cool.
Some mittens even get to take Pie out of the Oven!!!
Be glad it's not "midden" 
A fetus isn't an independent being until its born. Astrology is based on when you are born, an independent human, into this world.
Its very accurate if you have your chart done correctly.
There are some astrologers that will do charts based on the moment of conception, but I think they are iffy at best.
AV
I am a spork!
That's why I can't cut it.
I am pretty good at manipulation, though
That is why there is no way that astrology can be accurate by any means. Wouldn't the creation of life be more meaningful than rather when one was born? Conception is a magical process. Birth is simply the end of that process. Life doesn't begin when you are born, according to many, so why doesn't ones astrological sign fall to the moment life began rather than part way through it?
Oh Great! Now I'm an Ophiuchus. Are you an Ophiuchus, too?