Actually the modern chart is off by a few months. In my astronomy class we learned that the ancients greeks and romans were using a calendar that incorporated more months which meant like extra signs, which woud change the whole calender because the break off dates would be different.
My teacher went on to explain about the rotation of the planet and other changes that would effect the charts. Basically he had a lot of information that showed those charts are incorrect. I have a chart with all of this information on it when I find it I will post it.
In my eyes a person would have a better chance to gain insight by using something like this
http://www.pvv.ntnu.no/~raaness/astrology/#amon-ra
It's more effective to break down these attributes then apply them to your life, instead of believing you are a two-faced gemini or a stubborn goat capricorn. These symbols and attributes to not reflect our culture. If you look at OUR charts you will see that we are born to "high spirits" or deitys and this is what we reflect. Not fish, goats, or a two-headed beast.