I've heard this discussion before, one that broaches the topic of the wobble of the Earth's axis and the possible one-month "bump" in Sun Signs that resulted, making the Sun in, say, Aquarius rather than in Pisces.  I thought that this article was interesting, especially since it turned up in one of my local newspapers. The article, "The Stars Might Not Actually Be Aligned in Your Favor," avers that since the Earth wobbles (known as "precession"), the dates that we consider to be in a Sun Sign actually belong to another. In addition, others have proposed that since the ecliptic passes through the constellation Ophiuchus after Scorpio, the zodiac would now contain thirteen Sun Signs