Because of the obvious difference in the stars relative to a flat rather than spherical planet, there are some difficulties in translating Disc zodiac to Earth. The entire Disc Zodiac has sixty four signs, but A'Tuin is constantly moving through space, and the Disc Year is also roughly twice as long as ours (800 days barring freaks of magic, nature, reality- the usual stuff that means, occasionally, that afterwards people are more concerned about where and what they are before when). This means that, at present, only twelve signs can be applied to Earth without seeming just plain silly.