Luck Pillars (大運): The Ten-Year Seasons

The eight characters of a chart are fixed the moment you're born, and nothing that happens afterwards changes them.

What does change is the luck pillar. Every ten years a new one takes over: a stem and a branch laid alongside the chart and read against the same day master. In the last post I said BaZi keeps 命, what you were born with, apart from 運, the turn of time. The luck pillars, 大運, are the 運.

They're also the one part of BaZi that needs your birth sex, and the one part built on a piece of arithmetic that sounds arbitrary until you see where it comes from. Both are worth understanding before you read a single decade.

A month for every ten years

Luck pillars aren't a new set of characters. They're your month pillar, continued.

Start from the month you were born in and step through the sixty-pillar cycle one pillar at a time. Each step is a decade. Some charts step forward, into the months that followed their birth month. Others step backward, into the months before it.

The rate comes from one idea: a month of the calendar stands for ten years of a life. Thirty days to a decade, so three days make a year, one day makes four months, and a two-hour period makes about ten days. The classical rule is 三日為一歲, three days for a year, and it's the arithmetic behind everything below.

It also means the title of this post isn't a metaphor. Live to eighty and your luck pillars will have walked you through eight months of the calendar, nearly three seasons, starting from the one you were born in.

Same birth, two directions

Take the birth this blog has used before: 04:00 on 28 February 1990, in Seoul. Its pillars are 庚午, 戊寅, 甲子 and 丙寅. It's a Jia Zi 甲子 day, so the day master is 甲, yang Wood, born in 寅, the first month of spring.

Its luck pillars start from the month pillar, 戊寅. Here's where they go for a boy and for a girl born that same morning:

Read the branches down each column. His run 卯, 辰, 巳, 午, 未, 申, 酉, 戌: out of spring, through summer, into autumn. Hers run 丑, 子, 亥, 戌, 酉, 申, 未, 午: back through winter, then autumn, then into summer. One birth, two different walks through the year.

Which way you walk

Direction depends on two things: whether the year stem is yang or yin, and whether the person is male or female. The rule is 陽男陰女順行，陰男陽女逆行. Yang-year men and yin-year women go forward; yin-year men and yang-year women go back. 庚 is a yang stem, so the boy goes forward and the girl goes back.

The usual explanation is symbolic. Yang advances and yin retreats, so when your own polarity matches the year's you walk on into the months ahead, and when it doesn't you walk back through the months behind. There's no astronomy in it. It's a convention, an old one, and it means the timing layer of BaZi rests on an input the rest of the chart never uses.

On this site, birth sex enters exactly one calculation: which way your luck pillars run. The tradition also uses it to decide which relation stands for a spouse; this site reads the spouse palace, the day branch, instead. Leave the field blank and the luck-pillar section doesn't appear at all. There's no reminder asking you to fill it in. It simply isn't there.

When the first one starts

The first luck pillar doesn't begin at birth. The starting age, 起運, comes from the distance between your birth and the nearest month boundary in the direction you're walking: the next solar term that opens a month if you go forward, the previous one if you go back. The three-day rule turns that distance into years.

The boy walks forward, so he counts to 驚蟄, which fell at 05:15 on 6 March 1990, six days and an hour after his birth. Divide by three and his first luck pillar begins at two years old.

The girl walks back, to 立春 at 11:10 on 4 February, twenty-three days and seventeen hours before her birth. That makes seven years and eleven months. Same morning, same chart, and her first decade starts almost six years after his.

Three details decide the exact figure, and calculators don't all agree on them.

The moment you measure from. This site counts from the moment of birth itself. The true solar time correction changes which hour pillar applies, not when you were born. Some Korean practice measures from the corrected time instead, which moves the start by a few days at most.

How ages are counted. Here, from zero at birth. Some calculators give the same figure in East Asian reckoning, where you're one at birth, so their number runs a year or so higher.

How it's rounded. Some calculators round to whole years. This site keeps the months, because rounding the first boundary moves every boundary after it.

The same arithmetic is why an unknown birth hour blurs each handover by a couple of months, not by years: a whole day of uncertainty is only four months of start age.

Before the first pillar begins there's no decade to read, and for a young child the site says so plainly: until then, the natal chart and the month pillar govern on their own.

Reading a decade

A luck pillar is read the way everything else in a chart is read, against the day master. Its stem and its branch each stand in a Ten God relation to it, and the strength verdict decides whether that relation brings what the chart needs or more of what it already has.

Our example reads as strong, and what it needs is Earth: Wealth, somewhere for a well-supplied 甲 to spend itself.

Both columns in the table pass through the same ten stems. They meet them in opposite order. The two Wood stems, 甲 and 乙, are peers, and a peer competes with the day master for the very Earth it needs. The girl meets them in her decades from about twenty-eight to forty-eight. The boy meets them from fifty-two to seventy-two. Same stems, same pressure, twenty-four years apart.

And the stem is only half the pillar. Her 甲 decade is 甲戌, and 戌 is Earth: the competition arrives standing on the supply. His is 甲申, and 申 is Metal, Seven Killings, the relation that keeps a strong day master in check. The same stem on two different branches makes two different decades, which is why a decade is read as a whole pillar.

Readers split on the finer points. Some give the stem the first five years and the branch the last five. Others read the two together for all ten, and many weight the branch more heavily, since it carries the season. This site doesn't split the decade: each pillar holds for its full ten years.

The handover

The point where one pillar gives way to the next is 交運, the handover. The boy's fall at two, twelve, twenty-two and every ten years after; the girl's at seven years eleven months, then every ten years from there.

A reading on this site names its decade outright, by its pillar, and never calls it "your current decade," because the text is written once and read for years. Where you are inside the decade, how long is left, what comes next and how close the handover is are worked out fresh every time you open the page, and in the final year before a handover the page tells you. None of that is stored, because all of it goes stale. It's the same reason the table above gives ages rather than years.

The seasons you walk into

Inside each decade the years turn too. Every year has its own pillar, laid over the decade the way the decade lies over the chart, and that's the next post.

The chart is the season you were born in. The luck pillars are the seasons you walk into afterwards, one month of the calendar for every ten years of your life.