Free Bazi Calculator with True Solar Time
Enter your birth details to generate your Four Pillars chart — Day Master, Ten Gods, Hidden Stems, Five Elements, and Luck Pillars.
- No sign-up required
- Results generated instantly
- True-solar-time accurate
The tool
What this bazi calculator gives you
Enter a birth date, a time, and a city. The chart is computed in your browser, and you get the full working, not just the eight characters:
Four Pillars, fully annotated
Year, Month, Day, and Hour, each with its hidden stems, Na Yin, and growth stage.
Day Master and every Ten God
The character that stands for you, and how all the others relate to it, hidden stems included.
Five-element balance, counted twice
Once across the eight visible characters, once including everything hidden in the branches.
Branch and stem relations
Combinations, clashes, harms, and punishments, marked where they occur.
Shen Sha on the pillar they sit on
Ten symbolic stars, from the Nobleman to the Void, shown in place rather than as a list.
Luck Pillars and any year
Eight ten-year periods with the current one flagged, plus the annual pillar for any year you pick.
Your chart follows you into the guides
Open any guide from your result and it recognises your chart: the Day Master guide leads with your own stem, the Ten Gods guide marks the ones you actually have and where they sit, and the Shen Sha guide highlights your stars. The chart travels inside the link, so none of this needs an account.
Method
How we calculate your chart
Two bazi charts for the same birth can differ, usually because they use different conventions. Here is exactly what this calculator does with what you enter, so you can check it against any chart you already have.
What you enter, and why the city matters
The date and time come from your birth record. The city does two separate jobs: its longitude drives the true-solar-time correction, and its IANA time zone supplies the historical UTC offset, daylight saving included. That second part matters more than people expect — China ran daylight saving from 1986 to 1991, and a birth in those summers is an hour off without it. Leave the city blank and the chart still computes, but the hour pillar is less certain.
True Solar Time, worked through one example
Clock time is a political convention; the hour pillar was defined by where the sun actually was. We correct for both your distance from the zone meridian and the equation of time. A birth at 9:30 AM on 15 June 1990 in New York becomes 8:34 AM in true solar time — 56 minutes earlier, which moves the birth into the previous double-hour and changes the Hour pillar outright. You can switch the correction off in Advanced options and watch the pillar change back.
Where the boundaries are
Three boundaries decide the pillars. The month changes at solar terms, not on the first of a lunar month, and we compute those from the sun’s apparent longitude rather than a lookup table. The day changes at 23:00 by default, with midnight available as an option. The year changes at Li Chun by default, with Lunar New Year available. Whichever you choose, the result is shown with the convention it used.
Why another calculator may disagree
If your pillars differ somewhere else, work down this list: did it apply true solar time, does it roll the day at 23:00 or midnight, does it start the year at Li Chun or Lunar New Year, and did it know about daylight saving at your birthplace? One of those four explains almost every mismatch. Neither chart is wrong; they answer slightly different questions, and ours tells you which question it answered.
Verification
What this engine has been checked against
The chart is computed from your recorded local time and the conventions you choose, before any interpretation. Birth places resolve through 487 cities across 116 IANA time zones, so the historical UTC offset and daylight saving in force on your birth date come from the zone database rather than a fixed guess. Every result carries the conventions it used: the true-solar-time correction in minutes, the day boundary, the year boundary, and the exact luck-pillar onset.
Calculation coverage
Four Pillars and timing
True solar time from longitude and the equation of time, solar terms computed from the sun’s apparent longitude, a 23:00 or midnight day boundary, a Li Chun or Lunar New Year year boundary, and luck-pillar onset to the month.
Chart detail
10 Ten Gods applied to every visible and hidden stem, 30 Na Yin pairs, the twelve growth stages, 11 kinds of stem and branch relation, 10 Shen Sha stars, and void branches.
Reproducible evidence
6,000 randomly generated charts between 1901 and 2099 match tyme4ts on all four pillars, with zero mismatches; 800 luck-pillar onsets differ by an average of 0.01 months. Reference tables are checked entry by entry: 60 Na Yin, 120 growth stages, 100 Ten God pairs, and the hidden stems of all 12 branches, plus historical time-zone transitions against the IANA database.
You can run the same engine yourself: freebazi-mcp is an open-source Model Context Protocol server built on it, so you can compute a chart on your own machine and compare it with this page. Cross-checks are against tyme4ts; city coordinates and zones come from GeoNames (CC BY 4.0).
Next
Start reading your chart
Bazi (八字), the Four Pillars of Destiny, describes a person through the exact moment they were born. Once your chart is on screen, practitioners read it in a set order — and each step has a guide that opens with your own chart in it.
Find your Day Master
The stem of your day pillar stands for you; everything else is measured against it. All ten Day Masters →
Weigh the five elements
Which of Wood, Fire, Earth, Metal, and Water your chart is rich in, and which it lacks. The five elements →
Read the Ten Gods
Ten labels naming how each character relates to you: resources, output, wealth, authority, peers. The Ten Gods →
Follow the Luck Pillars
Ten-year periods that change what the same chart emphasises. Luck Pillars →
Questions
Frequently asked questions
Do I need my exact birth time?
No, but it changes how much of the chart is certain. With a time you get all four pillars. Without it, tick 'I don't know my exact birth time' and pick a double-hour if you have a rough idea: the year, month, and day pillars stay fully accurate, and only the Hour pillar and the details that depend on it are tentative. Your Day Master does not depend on the time at all.
Why do you ask for my birth city?
For two things, and you can skip it if you accept less precision. The city's longitude drives the true-solar-time correction, which can move the Hour pillar. Its IANA time zone supplies the historical UTC offset for your birth date, including daylight saving — China ran DST from 1986 to 1991, for example, and a summer birth in those years is an hour off without it.
What is True Solar Time, and why does it change my hour pillar?
True Solar Time is what a sundial at your birthplace would show. Clock time is a zone-wide convention, but the Hour pillar was defined by where the sun actually was, so we correct for your distance from the zone meridian and for the equation of time. A 9:30 AM birth in New York becomes 8:34 AM — 56 minutes earlier, enough to move it into the previous double-hour. You can switch the correction off in Advanced options.
Should I use the 23:00 or midnight day boundary?
Schools differ, which is why both are offered. The default is 23:00, the start of the Zi hour and the more widely used convention; midnight is available in Advanced options. It only matters if you were born between 23:00 and 00:59. If you were, try both and note how the Day pillar — and therefore your Day Master — changes.
Why does another bazi calculator show different pillars?
Usually one of four conventions: whether true solar time was applied, whether the day rolls at 23:00 or midnight, whether the year starts at Li Chun or Lunar New Year, and whether the tool knew about historical daylight saving at your birthplace. Neither chart is wrong; they answer slightly different questions. This one shows which conventions it used and lets you change them.
Can I check your calculations myself?
Yes. Every pillar is cross-checked against the tyme4ts calendar library, and the same engine is published as an open-source MCP server (freebazi-mcp) that you can run locally and compare against this page.
Can Bazi predict the future?
No system can guarantee future events, and this tool does not claim to. The calculation is reproducible arithmetic; the interpretation is a traditional framework for thinking about temperament, timing, and tendencies. Your decisions remain your own.