How a BaZi chart is built
Chinese timekeeping labels every year, month, day and two-hour period with a pair of characters from the sixty-pair cycle: one of ten heavenly stems (天干) and one of twelve earthly branches (地支). Four pairs make eight characters, which is what "ba zi" (八字) means.
- The year pillar changes at the start of spring, around 4 February — not at Lunar New Year.
- The month pillar changes at each of the twelve "jie" solar terms, around the 4th to 8th of each Western month.
- The day pillar follows an unbroken sixty-day cycle.
- The hour pillar covers two clock hours; the Rat hour runs from 23:00 to 01:00.
The Day Master
The stem of the day pillar is the Day Master (日主) — the element that represents you in the chart. Everything else is read in relation to it: what produces it, what it produces, what controls it, what it controls, and what is the same element. Those five relationships, each split into yin and yang versions, are the Ten Gods.
| Ten God | Relationship to the Day Master |
|---|---|
| Friend 比肩 / Rob Wealth 劫财 | Same element (same / opposite polarity) |
| Eating God 食神 / Hurting Officer 伤官 | The element the Day Master produces |
| Indirect Wealth 偏财 / Direct Wealth 正财 | The element the Day Master controls |
| Seven Killings 七杀 / Direct Officer 正官 | The element that controls the Day Master |
| Indirect Resource 偏印 / Direct Resource 正印 | The element that produces the Day Master |
Hidden stems and element balance
Each earthly branch contains one to three "hidden" stems (藏干) — its main element plus minor ones. The element bars count the visible stems and branches; switching on "include hidden stems" counts the hidden ones too, weighting the main one most. A chart where one element dominates or another is absent is the usual starting point for interpretation.
Luck pillars
From a certain age, each person moves through ten-year luck pillars (大运), which run forwards or backwards from the month pillar depending on the year's polarity and your sex. The age at which the first one starts is worked out from the number of days between your birth and the nearest solar term.
Time and place
Enter the clock time on your birth certificate. Strict practitioners adjust it to local solar time — which can differ from clock time by up to an hour or more depending on where you were born within your time zone, and daylight saving time — so a birth within half an hour of the edge of a two-hour period may belong to the neighbouring hour. If your time is uncertain, compare both.
Questions
What if I don't know my birth time?
Tick "I don't know the time". You'll get the year, month and day pillars, which still give your Day Master and most of the element balance.
What is the 23:00 option?
Schools disagree about the Rat hour. Some start the new day at 23:00 (the "early Rat"); others keep 23:00–24:00 on the same day. The default here keeps the day until midnight.
Is this a reading?
No. It's the chart itself, worked out accurately. Interpreting a BaZi chart is a craft in its own right, and practitioners often disagree.