I'll admit that I've never really followed astrological signs that much but apparently there is a debate about whether one should follow the sidereal or the tropical zodiac. Apparently if we follow the sidereal zodiac of Eastern origin, most of us would be under a different sign than we'd believed we were under all our lives. For example, my sign would no longer be Aquarius but Capricorn.
As I began to think of this, I remembered my first encounter with something of this nature. It arose out of my own genealogical research. I looked at my great grandfather's birth in his family Bible. The entries for each child read something like "Firstname" was born on "date" under the sign "name of sign." It was of course written in German script instead of English, but instead of seeing the standard tropical zodiac sign that I'd expected with his birth date, it gave a different one. As I began to examine the other members in his family, I knew that there was some other zodiac system in place because they all differed. My curiosity was peaked, and I had to do a little research to figure out exactly why all the signs were different. I discovered that the Amish used "moon signs" which were important for planting instead of the traditional astrological ones.
I believe that we'd all discover that we had three different signs if we chose to add the moon ones -- the traditional Tropical Zodiac signs of Western origin, the sidereal signs of Eastern origin, and the moon signs that were important to planting.