The second guy that I ever went on a date with was a big astrology believer. On our first date, he asked what my star sign was. He was cute, and I didn't want him to skip getting to know me on account of my birthday, so I told him that while I didn't believe in it myself, if he could accurately guess my sign based on my personality, I might be persuaded to believe.
The arrangement encouraged him to pay attention to my likes and dislikes, so I was pretty happy with my cleverness. A week or so later, he made his guess and was wrong. I told him that he could guess again next week, but he said that by not selling him my sign, I was disrespecting his "belief system." I told him that it was better to go through the trouble of getting to know someone instead of stereotyping people by their birth months. And so we broke up.
Why do people find astrology so convincing? At one point, I went though the signs and compared them to people that I knew well, and found no correlation at all between star signs and personalities. Scientific research into personality types has consistently found no correlation with various astrological systems as well.
I'm not even bothering with the idea that planetary alignments predict what's going to happen to someone next week.