A BaZi chart (八字, literally “eight characters”; also called the Four Pillars of Destiny) is built from the year, month, day and hour of your birth. Each of the four units is written as one Heavenly Stem plus one Earthly Branch — eight characters in total. Together they map your five-element balance, your Day Master, and the seasonal weather you were born into.
The Day Master is the Heavenly Stem of your day pillar — the one character that stands for you. Western astrology starts from your Sun sign; BaZi starts from your Day Master. Every other element in the chart is read in relation to it. There are ten possible Day Masters, one for each combination of the five elements and yin/yang.
It is not a defect. In traditional readings an absent element is the strongest lever in the chart: because you carry none of it, the moment it arrives — through a year, a place, a career, or a person — the whole chart moves with less friction. A thin element behaves much like a missing one, and is usually the highest-return thing to add deliberately.
Birth time gives you the fourth pillar, so without it your chart is three-quarters complete. If you don’t know the exact minute, pick the closest two-hour Chinese hour (子, 丑, 寅 …) — it is far more useful than leaving it blank. This calculator will still read your first three pillars if you skip the hour.
The calculation is deterministic — the same birth data always produces the same four pillars. Accuracy depends on data quality: birth date, birth time, and birth place (used for time-zone and true-solar-time correction). Everything is computed locally in your browser. The free chart uses traditional month boundaries; the paid reading applies true solar time and exact solar-term boundaries.
No. Your zodiac animal comes from the birth year alone — one of twelve animals. BaZi is the whole chart: four pillars, eight characters, five elements, and ten gods. The animal is roughly one-eighth of a BaZi chart. Most Western readers know the animal and have never seen the other seven characters.