NASA didn't "change" the astrological signs. Precession of the earth's orbit caused it.
Ancient astrologists picked the "signs" 2,000 years ago. A lot has changed since then.
I've found articles about this as far back as 2007. I've surprised several people with this trivia in the past few years, explaining that they weren't born under the "sign" they thought.
And if anyone really thinks NASA is taking this seriously, the "announcement" was a "fun fact" posted on a web portal intended for children.
As far as I know, this is the first time NASA itself has addressed the topic:
http://nasa.tumblr.com/post/150688852794/zodiac
One would think that anyone trying to make a deal out of these constellations would notice when the sun, moon, etc. are “in” them and go according to that.