Saju

Saju literally means "four pillars". Each pillar is a pair of characters drawn from an old Chinese calendar, and one pillar is assigned to each of the four units of your birth moment: year, month, day and hour.

Because each pillar has two characters, four pillars produce eight characters in total — which is why the same system is called Bazi ("eight characters") in Chinese. Korea has used it since roughly the fourteenth century, and it remains ordinary there: people check it before marriages, business launches and moves.

It is not the Chinese zodiac, and it is not Western astrology. It uses no planets and no constellations. It uses the calendar.