How We Calculate Your BaZi Chart

The year and month pillars change at the exact moments of the solar terms, which we compute to the second with an astronomical calendar algorithm. A BaZi year starts at the instant of Li Chun, usually on February 3 or 4, not on January 1 and not on Lunar New Year. So someone born on February 3 often still has the previous year's pillar.

Months work the same way. Each BaZi month begins when its solar term arrives (Li Chun, Jing Zhe, Qing Ming, Li Xia and so on), not on the first day of a lunar month. If you were born on the day a term changes, we compare your actual birth time with the exact moment of the term, so a single minute can change the month pillar.

If you enter a lunar birth date, we convert it to the Gregorian calendar first. For births in Seoul we use the Korean lunar calendar, because the Korean and Chinese lunar calendars occasionally differ by a day.

Clock time is first converted to standard time using your birthplace's time zone and the daylight saving rules in force that year. Historical daylight saving (for example in the United States, the United Kingdom, mainland China from 1986 to 1991, or Taiwan in several periods) is handled automatically from the time zone database, so you never subtract an hour yourself.

True solar time is the time set by the sun's actual position over your birthplace: the longitude correction plus the equation of time. Every degree of longitude is worth 4 minutes. Los Angeles, at about 118.2° W, sits about 7 minutes ahead of its 120° W zone meridian; London, at 0.1° W, is almost exactly on its meridian. The equation of time is a seasonal drift caused by Earth's orbit, ranging from roughly minus 14 to plus 16 minutes over the year. We calculate it with the standard astronomical formula, which stays within one second of the reference values.

When you choose a birth city, true solar time is on by default; you can switch it off to use the clock time, and without a city we use the clock time. If you were born close to the boundary between two double hours (for example 12:55 or 15:05), switching it on or off can change the hour pillar, so cast the chart both ways and compare. You can also cast a chart without a birth time: we use the year, month and day pillars only, and wherever the missing hour could change a conclusion (for example strength right on the line), the reading lays out each possibility.

For births between 11 p.m. and midnight there are two traditions: change the day at 11 p.m., or change it at midnight (the early and late Zi hour). You can choose on the chart page; the default changes the day at 11 p.m.

Luck pillars run forward for men born in a Yang year and women born in a Yin year, and backward for men born in a Yin year and women born in a Yang year. Years whose stem is Jia, Bing, Wu, Geng or Ren are Yang; Yi, Ding, Ji, Xin and Gui years are Yin.

The starting age follows the traditional rule of three days to one year: going forward, we measure from your birth to the next solar term; going backward, from the previous solar term to your birth, and convert every 3 days into 1 year, to the minute. The page shows your age in completed years and the calendar year each luck pillar begins, so you can see which one you are in now.

Strength depends on whether the Day Master is in season, rooted and supported. The code adds up the weight of every stem and hidden stem in the four pillars, works out how much of the chart belongs to the Day Master's own element (Peers) and the element that produces it (Resource), and checks whether the birth month is the Day Master's strong season. Charts that sit right on the line between strong and weak are marked borderline, and the reading explains both possibilities.

The chart structure (ge ju) follows the Zi Ping Zhen Quan method and is taken mainly from the month branch: in Yin, Shen, Si and Hai months the main hidden stem sets the structure, and in mixed months (Chen, Xu, Chou, Wei) the hidden stem that shows on a heavenly stem decides it. In October 2026 we checked 116 example charts from that book, and our structure matched the book in 91% of them.

Favourable elements are chosen mainly by balance: a strong Day Master is helped by elements that drain, control or use up its energy, and a weak one by elements that produce or support it. Then we adjust for the season: in a winter chart short of Fire, Fire becomes favourable; in a summer chart short of Water, Water does; and in spring and autumn we take the one character the Qiong Tong Bao Jian names for that Day Master in that month, as long as it does not work against the balance. Special structures such as follow charts and dominant charts are judged separately.

We checked strength against 51 example charts from the Di Tian Sui and agreed with the book in about 70% of them. Most of the disagreements were charts right on the line, which is why we mark borderline cases.

We compute every relationship among the eight natal characters, and between the chart and each luck pillar, year and month: stem combinations and clashes; six combinations, three combinations, half combinations and directional groups among the branches; clashes, harms, breaks, punishments and self-punishments; and pillar echoes and reversals, a year repeating its luck pillar, and filling an empty (void) branch. We also show which pillar is involved, because the year, month, day and hour pillars stand for roots, career, partner and later life.

The chart page lists 47 common symbolic stars (shen sha), auspicious, neutral and cautionary alike. Cautionary stars are always written as what to watch and what to do, never as something that will happen. If you ask about a star we don't chart, the reading says we don't chart it here, rather than telling you that you don't have it.

Each year runs from Li Chun and each month is cut at its solar term; the page shows months as Gregorian spans such as early February to early March. A month's rating starts with whether its stem and branch are favourable elements for you, then adds or subtracts for clashes and combinations with your day, month, year and hour branches, for clashes, combinations, punishments and harms with your luck pillar and the year itself, for pillar echoes, and for completing a three-branch combination with your chart.

For relationships we look at three things: whether the year or month clashes or combines your partner palace (the day branch), whether your partner star (Wealth for men, Officer for women) arrives or comes under pressure, and whether the partner star sitting in your current luck pillar gets clashed. For career we look at the month branch, Officer and Resource stars and the Travelling Horse; for money, the Wealth stars and Peers.

We only say that something is likely to happen in a given window when at least two separate signals point to the same thing. With a single signal, we only describe the mood of that period.

Once the code has finished, it packs the pillars, strength, structure, favourable elements, clashes and timing windows into a brief for the AI. Geumeum, our reader, can only answer from that brief: it never casts the chart itself and cannot add years or windows the brief doesn't contain.

The limits of a reading are written into the code too: no lifespan estimates, no predictions of disasters, lawsuits or divorce, no selling of remedies or lucky objects. On health, a reading only says which areas need care and how to look after them, never that you will fall ill in a certain year. Every reading is checked once more before you see it, and specific dates, percentages and alarming wording are filtered out.

The calendar part of how BaZi is calculated is shared by every school, so with a correct birth time the four pillars should come out the same anywhere. The usual reasons they don't are whether true solar time is used, how births between 11 p.m. and midnight are dated, and whether the birthplace's time zone and daylight saving are applied. Line those three up and the pillars nearly always match.

Differences in interpretation come from schools of thought: some lead with seasonal adjustment, others with balance, and each keeps its own list of symbolic stars. We lead with balance and add seasonal adjustment, and this page sets out all of our rules. BaZi describes tendencies and timing, not a fixed fate; what you do with them is up to you.