The Four Pillars

八字 BāZì, your birth written as four pillars of stem and branch.

Year, month, day and hour each take a Heavenly Stem and an Earthly Branch. The day’s stem is your Day Master, the character that stands for you, and the year’s branch is the animal you already know. It also gives you the element the popular zodiac usually leaves off: not just Dragon, but which kind.