Four Pillars calculator on true solar time
Most BaZi calculators read the clock on the wall. This one rebuilds the birth moment from the historical timezone rule, your longitude and the equation of time, then draws the four pillars from that instant — and shows you every step so you can check it.
Your birth details
Advanced settings
Equation of time Adds the sun's seasonal drift, up to about 16 minutes.
Use my own coordinates For towns missing from the list, or someone born at sea.
Want a full reading of these four pillars? Send the chart on WhatsApp and we will take it from there.
Every figure above is reproducible: the timezone rule, the longitude offset and the equation of time are listed in order, so anyone can check the working.
What the calculator does, in order
- Reads the clock as local wall time. You enter what the clock actually said at the place of birth.
- Applies the timezone rule in force that day. This covers standard time, daylight saving and the historical changes to both — for example China summer time of 1986 to 1991.
- Adds the longitude correction. A zone has one central meridian; being away from it shifts solar noon by four minutes per degree.
- Adds the equation of time. The sun runs fast or slow through the year by up to about sixteen minutes.
- Draws the pillars from the corrected instant. The year changes at lichun, each month at its solar term, and the hour branch every two hours.
Worked example. Born in Beijing on 1 June 1988 at 12:00 by the clock. China was on summer time that day, so the offset in force was UTC+09:00, which anchors the zone to 135°E, and Beijing sits 18.6° west of that meridian. With the equation of time, the true solar time is 10:48. The hour branch moves from wu (11:00–12:59 on the clock) to si, and the hour pillar changes from bing-wu to yi-si — a different pillar from the one most calculators would show.
Reading your result
The four columns are the year, month, day and hour pillars. Each is a pair: a heavenly stem above an earthly branch. The stem of the day pillar is the day master — the reference point a reading is built around.
Under the pillars you will see the elements carried by each stem and branch. That count is a map, not a score: it shows what is present in the chart, and the reading asks which of them are supported and which are crowded out. Two people with the same count can have very different charts, because position and season matter as much as totals.
If the wall-clock chart and the solar-time chart differ, the comparison line spells out both, so you can see exactly which pillar moved and why.
Worked examples
| Birth (clock) | Place | True solar time | Hour pillar on the clock | Hour pillar corrected |
|---|---|---|---|---|
| 1988-06-01 12:00 | Beijing, China | 10:48 | 丙午 | 乙巳 |
| 1990-08-01 09:00 | Shanghai, China | 07:59 | 丁巳 | 丙辰 |
| 1988-07-15 14:30 | New York, USA | 13:28 | 乙未 | 乙未 |
| 1995-03-20 23:40 | Singapore | 22:27 | 戊子 | 丁亥 |
The last row is the late zi hour: shortly before midnight the true solar time falls back into the previous two-hour branch, and the hour pillar changes with it.
Frequently asked questions
Why does this calculator ask for a city instead of a timezone?
Because two things depend on the place, not just the zone: the longitude, which sets how far the sun is from the middle of your timezone, and the historical timezone rule, which decides whether daylight saving was in force on your birth date. A city gives us both. If your town is not in the list, switch on manual coordinates and type the longitude and zone yourself.
What is true solar time, in one sentence?
It is the time a sundial at your birthplace would have shown at that moment: your clock time corrected for the zone you were in, your distance from that zone central meridian, and the seasonal drift of the sun known as the equation of time.
Does the equation of time really change the chart?
It can. The correction swings between about -14 and +16 minutes across the year. BaZi hour branches change every two hours, so if your birth time sits within about a quarter of an hour of a branch boundary, that swing decides which hour pillar you get.
My birth time is 23:30. Which day is my day pillar?
Schools genuinely disagree. One line keeps the day pillar on the birth date, the other rolls it to the next day, because the zi branch straddles midnight. Both options are in Advanced settings; pick the one your existing readings use, and note that the choice changes the day pillar, the hour stem and the day master.
Why does a city in western China show Beijing time?
China keeps one official clock, Beijing time at UTC+08:00, from Xinjiang to Shanghai, and birth records follow that clock, so every mainland city is read on it here. The timezone database also records an unofficial Xinjiang time of UTC+06:00. If your family kept that clock rather than the official one, switch on manual coordinates and choose Asia/Urumqi, which shifts the calculation by two hours.
Should I enter the clock time or the adjusted time?
The clock time, exactly what a clock on the wall read at that place and date, including any daylight saving that was in force. The calculator handles the rest and shows you each step.
Which charts does this match?
The pillars come from published solar-term tables, so the year, month and day boundaries follow the standard astronomical definitions: the year changes at lichun, the month changes at each jie solar term, and the day follows the sexagenary cycle. The output matches any calculator that uses true solar time with the same day-boundary convention.
Is a BaZi chart a prediction?
No, and we will not pretend otherwise. BaZi is a traditional Chinese framework for reflecting on character and timing. Treat the chart as a lens for thinking, not a forecast, and never as medical, legal or financial advice.
Not sure what the chart means?
The what is BaZi page explains what each pillar represents, and the true solar time page goes through the astronomy behind the correction. Both are written for people who have never had a chart read before.