Why does previous literature say I'm an Aquarius and the natal charts (3 of them now) all say I'm a capricorn?

So basically I was born on Jan. 20, 1988. Most all literature I've read up to this point says that I am an Aquarius yet I've gotten natal charts from alabe.com, astro.com, and cafeastrology.com and they all tell me my sun sign should be a capricorn. I realize I'm like smack-dab in the middle of a cusp but for some reason these readings just dont seem quite right. There are some similarities but I see more similarities when I look at the personality of an Aquarian. The whole concept of myself being a Capriquarian would make sense seeing as how I see qualities of both but it seems like the Aquarian is the more dominant. Could it be because of the relativity of calendar dates? The fact that every year the planets are "drifting" and rotating in a wider and wider ellipse? Any feedback would be great!