準 · accuracy
How accurate is this chart?
A Four Pillars chart is only as good as its calendar. Small shortcuts, like treating every month as 30 days or using today’s time zone rules for a birth in 1973, quietly move people into the wrong pillar. This is exactly what we calculate, and how.
1. The month changes at a solar term, not on the 1st
Ba-Zi months begin at the twelve jié (節) solar terms, the moments the sun reaches fixed points on its path. We use a table of those moments, to the minute, covering the years 1899 to 2100, instead of a rough calendar date. Someone born the day a term arrives is placed by the actual moment, not the day.
2. Time zones and daylight saving are historical
Your birth time is converted using the real rules in force where and when you were born. A birth at noon Central Time in 1973 is not the same moment as a noon birth under today’s rules, and the chart depends on that moment. We use the standard historical time zone database, so daylight saving changes are applied for the year of your birth.
3. Luck pillars are counted to the day
Your 10-year luck pillars run forward or in reverse depending on the polarity of your birth year and your sex at birth. The first one begins at an age we count exactly: the days from your birth to the nearest solar term, at three days per year. You see it as years, months and days, not just “about 8”.
4. Ten gods and hidden stems, per pillar
Every pillar shows its stem’s ten god, and the stems hidden inside each branch with their own ten gods. We check our ten-god logic against the engine itself: in our own testing across about a thousand values on randomly chosen births in several time zones, they matched every time.
5. A hexagram for every pillar
Each pillar also maps to an I Ching hexagram through its stem and branch, so the chart connects to the Book of Changes in a way plain calculators do not. Read the 64 hexagrams in our Learn section.
Birth place and “sun time”
Some practitioners shift the clock to the sun at the birth place (local mean or true solar time). That is a tradition, not a requirement, and it can move the hour pillar. By default we do not apply it. If you enter a birth city you can try it as an extra and see the difference.
What we do not claim
Ba-Zi is a traditional wisdom system. It describes tendencies and the character of a period, not a fixed future. We do not claim scientific validation, and nothing here is medical, financial or legal advice.