THE GOAL-GETTING, MOUNTAIN-CLIMBING, SERIOUS BUSINESS SIGN OF THE ZODIAC. A Capricorn is the ultimate in productivity. If you're born between December 22 and January 19, you're a Capricorn - which means you're wired to climb the corporate ladder, achieve goals like you're on a mission, and maybe stress-eat a few extra papers. Capricorns are an Earth sign ruled by Saturn (the planet of rules), so expect them to be practical like accountants, ambitious like they're running a marathon, and serious like they're at a board meeting. Don't expect Capricorns to slack off - they're too busy leveling up.