People with zodiac tattoos take heed: your astrological sign probably isn’t what you think it is. In an article for LiveScience, Pedro Braganca tears down some commonly held notions about the signs of the zodiac. Braganca writes that astrological signs were determined 2,200 years ago, based on the position of the sun in relation to the constellations. The problem is that the alignment of the stars has changed over time. Since the astrological positions were first recorded, the Earth has shifted on its axis due to a natural phenomenon called precession, caused by the Moon’s gravitational pull on the Earth’s equator. “This [shift],” writes Braganca, “means that the signs have slipped one-tenth—or almost one whole month—of the way around the sky to the west, relative to the stars beyond.” In other words, your actual astrological sign is probably not the one you thought it was. It may be the one directly before. If you think you are a Cancer, chances are you’re actually a Gemini. If you’re still interested, try LiveScience’s Starry Night program to determine your real, astrologically consistent zodiac sign.