You enter the clock time to the minute and your birthplace. We look up the clock offset actually in force on that date (Singapore and Malaysia ran on UTC+7:30 until 1982 and UTC+9 during the occupation; China, Hong Kong and Taiwan had summer time in some years), then correct for longitude and the equation of time to get true solar time. In Singapore the clock runs 48 to 79 minutes ahead of the sun, enough to change the double hour for more than half of births. Schools differ on this, so clock time is available as a setting, and births within 15 minutes of a double-hour boundary are flagged with the neighbouring chart one tap away.

The date is converted to the Chinese lunar calendar. The year changes at Chinese New Year (正月初一), not at Lichun, which is the BaZi rule. A birth in the second half of a leap month (day 16 onwards) counts as the following month. A birth between 23:00 and 23:59 counts as the next day's Zi hour by default, as most schools do; the same-day rule is a setting.

Starting from the Yin position, count forward one palace per lunar month, then backward one per double hour. Where the count lands is the Life Palace. The Body Palace uses the same month count but moves forward with the hour instead.

From the Life Palace, the remaining eleven palaces are laid counter-clockwise in fixed order: Siblings, Spouse, Children, Wealth, Health, Travel, Friends, Career, Property, Fortune, Parents.

The Life Palace acquires a heavenly stem from the birth year via the five tigers rule. That stem-branch pillar maps through the Na Yin table to one of five bureaus: Water 2, Wood 3, Metal 4, Earth 5 or Fire 6.

The lunar day is divided by the bureau number; the quotient and remainder fix Zi Wei, and its series follows at fixed offsets. Tian Fu mirrors Zi Wei across the Yin-Shen axis and its series fans out from it.

The fourteen auxiliaries (Wen Chang, Wen Qu, Zuo Fu, You Bi, Lu Cun, Qing Yang, Tuo Luo, Tian Kui, Tian Yue, Huo Xing, Ling Xing, Di Kong, Di Jie, Tian Ma) and 38 secondary stars such as Hong Luan, Tian Xi, Tian Yao and Tian Xing, plus the twelve life-stage (长生) markers.

Every major star is graded by its seat, from Temple (庙) through Prosperous, Favoured, Beneficial and Neutral to Weak and Fallen (陷). The same star reads very differently at Temple and at Fallen, so brightness feeds every reading.

The birth-year stem selects four stars for Lu, Quan, Ke and Ji. Each palace's own stem also sends its four transformations across the chart (飞化), and where a palace transforms a star inside itself we mark a self-transformation (自化).

Around forty classical structures (格局) are checked, from 君臣庆会 and 石中隐玉 to 羊陀夹忌, and each one is shown with the exact chart evidence that triggered it.

The bureau number sets the starting age, counted in nominal age (虚岁), as the classical method does. Yang-year males and yin-year females run the decades clockwise; the others counter-clockwise. Each decade palace carries its own stem for decade transformations and becomes the Life Palace of its ten years.

The annual cycle follows the lunar year. The year's branch picks the annual Life Palace, its stem fires the annual transformations, the annual moving stars (流曜) are placed, and the minor limit (小限) for your age is read alongside. The months are seated from the Dou Jun.