How this calculator computes a bazi chart

The calculator takes a birth date (required), a sex (required — it sets the direction the luck pillars run, a rule of the system, not a product choice), and a birth time (optional). Four fixed conventions govern everything downstream:

• The year turns at Li Chun (立春, around February 4), not at Chinese New Year. Bazi is a solar system: the month pillars are keyed to the 24 solar terms too. A birthday in late January or early February can therefore sit in a different year pillar than the popular zodiac would suggest. (why the year begins here.)
• True solar time, when you give us a birth city. Hour pillars are keyed to the sun, not to a clock, and two modern layers sit between them: the time-zone offset in force that day, and the gap between your longitude and your zone's meridian. Given a city we undo both, which also removes daylight saving without asking you to remember whether it applied. Without a city we read the clock reading literally, say so on the result, and flag it when the time sits within about 45 minutes of a two-hour pillar boundary. We do not apply an equation-of-time term; that is a further refinement of up to about 16 minutes which we currently leave out. We measured how eight other implementations handle this and the three other conventions that move a chart: why bazi calculators disagree.
• No birth time → an honest three-pillar chart. The year, month, and day pillars do not depend on the hour, so they are computed exactly; the hour pillar is dropped rather than guessed, and the strength test renormalizes to five positions (base 76) instead of seven (base 100).
• Nothing entered is stored. The chart is computed and shared by URL only; there is no account and no server-side record.

Each pillar is one heavenly stem over one earthly branch. The year pillar comes from the Li-Chun-bounded year; the month pillar from the solar term, its stem fixed by the year stem (the 五虎遁 rule); the day pillar from the continuous sexagenary day count; the hour pillar, when a time is given, from the day stem (the 五鼠遁 rule). Each branch also carries one to three hidden stems — the elements buried inside it — which the strength test in Step 2 reads. This derivation is handled by the tyme4ts library and is not where any interpretation happens yet.

The day master is the day pillar's stem — the one character read as you. Everything else is scored by whether it supports that character. The test comes from Wei Qianli's 1935 Qianli Minggao: does the day master get seasonal support, does it root in the branches, do other stems stand with it? We quantify those three factors with the position weights standardized in modern teaching — the month branch counting heaviest, because season is the classical test's single biggest factor:

* Hour stem and branch count only when a birth time is given; without it the base is 76.

A position counts as support when its element is the day master's own element (a Companion) or the element that generates it (a Resource). A stem contributes its full weight; a branch contributes its weight scaled by the strength share of each supporting hidden stem. Those shares follow Zhu Zuxia's 1999 lineage over the standard Yuanhai Ziping hidden-stem table:

Add the supporting points, divide by the base. At or above 50% the chart reads strong; below 50%, weak. Between 40% and 60% it is treated as near-balanced: the reading still resolves to strong or weak, but every year's swing is damped to 60% of its size and the chart is flagged as a close call, because at that margin a stricter or looser practitioner could land on the other side.

Strength is only an input. It flips a single rule from the Yuanhai Ziping: strengthen a weak day master, drain a strong one. That decides which of the five elements help this chart and which press on it — the switch every year score is then measured against.

v1 weights the favorable elements equally rather than singling out one 用神 (governing favorable element); that refinement is noted as a known simplification.

Luck pillars are ten-year stretches that set the weather each year is scored against. Their direction — forward or backward through the sexagenary cycle — follows the classical rule of year-stem polarity crossed with sex, and the age they start is taken from the chart's decade-fortune count (a nominal 虚岁 age). Each pillar is then marked favorable or not by the same element rule as a year:

pillar offset = (stem favorable ? +8 : −8) + (branch's main element favorable ? +10 : −10)
favorable pillar = offset > 0

The branch weighs more than the stem here, which is why a decade takes on the character it does, and why the chart reads in ten-year chapters rather than as noise. That decade offset (from −18 to +18) is carried into every year that falls inside the pillar.

Each year gets one number — the close, the body of the candle on the chart. It starts at a neutral baseline of 50 and adds three swings: the decade context it sits in (weightiest, the classical "大运为重"), the year's own stem, and the year's own branch. If the chart is near-balanced, the whole swing is damped to 60%.

year stem = favorable ? +6 : −6
year branch = favorable ? +8 : −8  (by its main hidden element)
decade = the luck-pillar offset above (0 before luck pillars start)
close = clamp(50 + (decade + year stem + year branch) × damp, 5, 95)
open = the previous year's close

The close is the body; the wick is volatility. The year's branch is checked against each of the natal branches for the four classical branch relations. Each adds an amplitude; the high is the close plus the total, the low is the close minus it, capped at 15. When one pair could be read more than one way, the stronger relation wins, in the order clash > punishment > harm > combination.

Two day-branch-anchored stars are also marked when the year's branch matches: the peach blossom (咸池, romance and charm) and the travel horse (驿马, movement and relocation). They label a year; they do not move its score.

OHLC, defined: open = last year's close · close = the year's combined score · high = close + wick · low = close − wick. Borrowed from a candlestick chart so a life reads at a glance, but every candle opens to show the three components that built it.

From the year-by-year scores the engine reads a few summary facts, all by plain arithmetic on the series: the peak decade is the highest-averaging rolling ten-year window; a golden run is consecutive favorable decades merged into one long stretch; the best and hardest past years (adult years only) are the series' high and low behind you — the checkable, backtestable claims; and the next turn is the next decade pillar that changes sign, up or down. Nothing here is a separate model; it is all the same series, read.

Elon Musk, born June 28, 1971. Birth time unpublished, so this is an honest three-pillar chart — the same one used elsewhere on this site, and computed live by the same engine for the figures here.

1. Day master: Jia Wood — a Yang Wood day master.
2. Strength: 19.6 of 76 supporting points = 25.8%, under the 50% line, so the chart reads weak. The heaviest single position — the month branch at 40 — contributes nothing here, and one correctly weighted position outvotes the rest.
3. Favorable elements: a weak Wood day master wants company and feeding, so the favorable elements are Wood and Water.
4. A scored year — 2018: an unfavorable year stem (−6) over an unfavorable branch (−8), inside an unfavorable decade (−18):

close = 50 + (−18 decade − 6 stem − 8 branch) = 18

18 is the lowest year on Musk's chart — and 2018 is the year he has publicly called the most painful of his career. Same three numbers, added in the open, landing on the year he names himself. For contrast, the chart's peak decade computes to 2002–2011, the stretch that built the whole enterprise. None of this is tuned after the fact; it is the specification above, run forward.

The specification is deterministic, but it is not the only valid one, and it is not science. Three limits are worth stating plainly:

• One school. This is the strengthen-and-balance approach with a modern scoring simplification. Pattern-school and blind-school readers weigh the same chart differently and would sometimes reach the opposite conclusion.
• Near-follower charts. When support is very low, a chart can cross from "weak" into a follower (从) pattern, where the favorable elements invert. Musk's chart, at roughly a quarter support, sits near that line — a real example of where schools would part ways.
• Known misses, recorded honestly. Backtesting against public lives, the decade-level reading lands well, but single years miss: Musk's 2021 (a peak public year) scores low on this method, and a follower-pattern reading would score it high. The chart is strongest at the ten-year scale and should be read that way.