A Computational Mapping of the BaZi Major Luck Cycles

　　Establishing major luck cycles in BaZi is a rather distinctive method of numerological computation. Depending on the sex of the person and whether they were born in a yin or yang year, one counts forward or backward to the solar-term boundary, totaling the number of days, and takes three days as one year of luck.

　　Because there are fifteen days on either side of a solar term, whether counting forward or backward the total is only thirty days; with three days making one year, this amounts to ten years in all.

　　From the major luck cycle one can see that in fact major luck simply changes by month—if counting backward, then assign the backward-counted months successively as ten-year cycles, and vice versa.

　　Usually whether counting forward or backward, it rarely exceeds a single year, so generally major luck is set for twelve months, i.e. 120 years (in fact the computation can continue).

　　Here a rather interesting mapping arises: the entire 120 years are essentially mirrored out by cycling one full round forward or backward from the starting stems and branches.

　　What does this mean? It means that major luck is in fact still determined by the year—once one is born in a given month of a given year, the trend of the major luck cycles before and after is already fixed.

　　Put differently, a microcosm of one's whole life is actually embodied in the year of birth; yet in ordinary fate calculation one often judges strength and weakness by the day pillar, and what changes is treated as the major luck. This way of thinking is actually exactly reversed.

　　BaZi also has a method of establishing minor luck: based on the birth day, assign the hours forward or backward. The pattern is the same, but one minor luck period governs one year of age.

　　Looking at the model of major luck: the month used within major luck maps to ten years, and this ratio follows three days making one year. Why should three days govern a year? Because in Taiyi, three days tour one palace; three days is also exactly thirty-six double-hours—exactly one-tenth of the three-hundred-sixty cycle. Hence one month can govern ten years.

　　If one maps days to years, the same proportional scaling should be applied in order to achieve normalization. One day is twelve double-hours; to convert this to 360, each double-hour must be multiplied by 30, so we get:

　　Taiyi's three days touring one palace can represent one year—this is first fixed. One day is one three-hundred-sixtieth of a year; three days are one one-hundred-twentieth.

　　Proportionally, one one-hundred-twentieth of a day can represent one year. Within one day there are twelve double-hours, and each double-hour can be divided into ten ke—so it should be one ke that represents a year, not one double-hour.

　　But this conflicts with major luck, which has ten stem-branch pairs—clearly not what we need. So it must be changed. How?

　　We know above that three days as one year equals thirty double-hours; if we treat each of those thirty-six double-hours as ten ke, they become 360 ke. Within 360 ke, if three ke make one year, then thirty ke make ten years. Ten years are one hundred twenty months, so ten ke can represent forty months—thus one double-hour can represent forty months, i.e. three years and four months. This can serve as the mid-luck of BaZi; because of the month offset, it can accurately position things before and after.

　　The above is only theory, not yet verified by evidence—do not take it too seriously.