Read the four pairs before interpreting them
A Four Pillars chart assigns a stem–branch pair to the year, month, day and hour. The resulting eight characters give BaZi its name. Joey Yap’s introductory account uses the day stem, called the Day Master, as the reference for comparing the other chart characters.
In the explorer, select a pillar to inspect its full pair. Keep the stem and branch distinct: the Day Master is the day stem, while the day branch remains another part of that pillar. The report retains all four pairs even when you focus on one column.
Joey Yap · Four Pillars and Day Master (modern practitioner account) ↗
Choose the clock and the day boundary
Enter the recorded birth date, local time, place and timezone. When a legal clock repeats an hour, record which occurrence is intended. This introductory report requires an exact-time calculation; it does not turn an unknown time into an hour pillar.
Atlas offers civil time, local mean solar time and local apparent solar time. Each can be paired with a day beginning at midnight or at 23:00. The comparison table keeps the birth instant fixed and shows how these six conventions affect the displayed pairs. Agreement between rows does not prove that the recorded birth time is accurate.
The tool uses a Li Chun solar-year boundary and solar-term month boundaries. These settings belong to this named method. A lunar month or the Lunar New Year should not be substituted silently when checking a Four Pillars result against another service. Always compare the receipt as well as the characters.
Worked example: the same instant, two day boundaries
This is an original Atlas teaching example, using a synthetic record: 7 January 2000, 23:30, Greenwich, timezone UTC. Select civil time. With the midnight day boundary, the explorer gives Jia-Zi (甲子) for both the day and hour. Change only the boundary to 23:00: the day becomes Yi-Chou (乙丑), and the hour becomes Bing-Zi (丙子).
Zi still names the double-hour spanning 23:00–01:00. The hour stem changes because this Atlas method derives it from the displayed cycle day. HKO’s table assigns Jia to the Zi hour of a Jia day, and Bing to the Zi hour of a Yi day. This checks the relationship between the displayed day and hour; it does not establish every school’s late-Zi rule.
Some approaches distinguish early and late Zi differently. This tool does not implement a third option that retains one day pillar while taking the hour stem from the next day. Record the selected convention when saving or comparing the example.
Hong Kong Observatory · Gan-Zhi sequences and hour-stem tables ↗
Follow a reading from facts to interpretation
Begin with the input receipt and the selected day stem. Next, read the four pillar explanations and their qualifications. Their reflective questions are original prompts, separate from the attributed teaching. A paragraph should be read with the fact and convention that produced it.
Then inspect visible Ten Gods, hidden stems and main qi, branch pairs, and three-branch groups. These panels answer different questions. A listed branch combination is a membership result; it is not a finding that transformation has occurred. An incomplete group remains incomplete. Main qi is a category here, not a numerical percentage.
Use the source links and the glossary to examine the vocabulary of each layer. The native Chinese phase meanings should stay with this reading; a similarly named term from another system is not an interchangeable interpretation. Do not combine these introductory classifications into an unsupported overall score.
Save the calculation you actually read
After changing birth data or a convention, wait for the updated result before downloading. The HTML report and matching JSON retain the selected settings, calculated facts, readings, sources and glossary. Related concepts in the report link to the definitions captured with that report.
Email sign-in enables private saving with a title and notes. Reopening a saved report preserves its original receipt and wording. Editing a person’s birth profile does not silently replace that capture. A fresh calculation should be saved as a new result when you want to compare a correction or a different convention.
The current report does not determine Day Master strength, favorable elements, luck periods or a complete transformation analysis. Those require separate accepted methods. Its scope is an inspectable introductory reading, not a substitute for every BaZi school or a claim that symbolic interpretation has been empirically verified.
Calendar notation and interpretive practice
HKO describes Gan-Zhi usage for years, months, days and hours as developing at different times. A shared calendar notation does not establish a single origin date for all later Four Pillars teachings. This entry uses HKO for calendar tables and identifies Joey Yap separately as a modern practitioner source.
Hong Kong Observatory · Gan-Zhi sequences and hour-stem tables ↗Joey Yap · Four Pillars and Day Master (modern practitioner account) ↗
Word origin · etymology
English translation of a Chinese name.
Sìzhù, 四柱, means four pillars; Bāzì, 八字, means eight characters. Saju is the Korean reading of the four-pillar name.
How we know · epistemology
Calendar-derived interpretive framework
Four pairs are calculated from birth data under stated seasonal and clock rules. A date near a term or day boundary can change a pillar; the derived pattern is not a measured personality or a fixed life trajectory.
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Connected concepts
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Terms used in this explanation
Mentioned in 33 other entries
These links connect subjects and terminology. They do not establish a shared historical origin.
Sources & provenance
Use the citations beside each section to distinguish a calculation convention, a historical teaching and an editorial example.