Your chart is drawn from a traditional almanac called a manseryeok (만세력, 萬歲曆) — the "Ten-Thousand-Year Calendar" — which maps every day onto the cyclical calendar. Because that calendar is fixed, the calculation is deterministic: the same birth date, time, and place always produce the same Four Pillars. Nothing here is invented for you — it is arithmetic on a calendar.
The two building blocks
Every pillar is one Heavenly Stem above an Earthly Branch below.
- There are ten Heavenly Stems (천간, 天干) — the five elements, each in a yang and a yin form: 甲 乙 丙 丁 戊 己 庚 辛 壬 癸.
- There are twelve Earthly Branches (지지, 地支) — the familiar zodiac animals, each tied to an element, a season, and a two-hour block of the day: 子 丑 寅 卯 辰 巳 午 未 申 酉 戌 亥.
From birth moment to four pillars
- Year pillar — from the year of birth, reckoned by the solar calendar rather than the January-1 new year.
- Month pillar — from the solar term the birth falls in, so the month turns on the sun's position, not the calendar date.
- Day pillar — from the day itself; its stem is your Day Master.
- Hour pillar — from the two-hour branch of the birth time, adjusted to true solar time for the birthplace.
Two details matter for accuracy. The day is traditionally reckoned from about 11 p.m., not midnight, so a late-night birth can fall on the next day's pillar. And the hour depends on where you were born, because clock time and true solar time differ by location. If the birth time is unknown, the hour pillar is lost — but the Day Master usually survives, so a reading is still possible, just less complete.
That is the entire mechanism. It is standard, shared, and reproducible by anyone with a manseryeok — which is exactly why the craft is not in the calculation, but in reading what the eight characters mean.