About Pillars

What Pillars is

Pillars (Pilares in Spanish) is a BaZi app for phones, and this site is its web version. BaZi, the Four Pillars, turns the moment you were born into four pairs of Chinese characters: one each for the year, the month, the day and the hour. Pillars works them out for your birthplace, shows you the method and explains in plain words what they mean in the tradition. Every result shows where it comes from, so you can check it.

How it calculates

• True solar time. By default, Pillars uses the time the Sun showed where you were born, not the clock. It corrects for your longitude and for the equation of time, the few minutes the Sun runs ahead of or behind the clock over the year.
• Time zones as they were. To turn your birth time into universal time, it uses the IANA time zone database (tzdata 2026e), with each country’s daylight saving and time zone changes on each date. If your time fell in a clock jump or happened twice, it tells you.
• The Sun, calculated. The Sun’s position comes from the VSOP87D theory, with IAU 2000B nutation. It gives the solar terms, which mark where your BaZi year starts (at Lì Chūn, the Start of Spring) and where each month starts. The terms for 1900–2100 are built in.
• Not sure of your birth time? It works out every possibility and shows you what changes and what doesn’t.
• Conventions. Where schools disagree, Pillars picks one and says so. By default it uses solar time and starts the day at 11 pm, when the 子 (zǐ) hour begins.
• The calculation ID. Every chart carries a calculation ID (calc-…), a kind of fingerprint: it sums up your details, the convention, the method and the table versions. Two charts with the same ID came from the same calculation.

If your chart doesn’t match another app’s, it’s almost always a convention: Why other apps show a different chart explains.

The same engine as the app

The site has no calculation of its own. It runs the same code as the Pillars app, converted to work in your browser. A chart calculated here and in the app gets the same pillars, the same texts and the same calculation ID. An automated test compares the two on 3,000 sample births, and every change has to pass it.

Sources and checks

The tables follow the Zi Ping (子平) school, as the classics set it down:

• 淵海子平 (Yuan Hai Zi Ping)
• 三命通會 (San Ming Tong Hui)
• 子平真詮 (Zi Ping Zhen Quan)
• 星平會海 (Xing Ping Hui Hai)

Kua and the Eight Mansions follow the trigram rule of the 八宅明鏡 (Ba Zhai Ming Jing), and the year’s flying stars follow the annual chart of 玄空飛星 (Xuan Kong Fei Xing). The links between the elements and the organs come from traditional Chinese medicine, and they’re shown as a traditional view, not as medical advice.

Every table is pinned down by an automated test and was checked in one of these ways:

• the pillars, against the independent lunar library (6tail): 6,000 random moments, with no differences;
• the solar terms, against the Swiss Ephemeris: within 3 seconds;
• the symbol tables (Na Yin, hidden stems, the ten roles and the life stages), against the same lunar library;
• the stars, against the classical rhymes they’re taught with; the clashes and combinations, against published tables; and whole charts, against published charts.

Where schools differ, on some stars or the Life Palace for instance, Pillars uses one variant and documents it.

The texts

The reading texts and the articles were written for Pillars, in Spanish and in English, each language on its own rather than translated. They’re traditional interpretations, not classical tables, and a practitioner hasn’t reviewed them yet. Every reading says where it comes from: your chart, the traditional reading or the app’s model. The 1-to-5 ratings come from the app’s model, a rule of our own, and they carry its name.

Places and fonts

• Places: GeoNames, under the CC BY 4.0 license. The city search runs in your browser.
• Fonts: Figtree, Cormorant Garamond and Noto Serif TC, under the SIL Open Font License, served from this site.

Privacy

Everything is calculated and stored in your browser. There’s no account and no server with your birth details. The details are in the Privacy policy.

Before you read

Pillars offers traditional BaZi interpretations as a guide for reflection. It isn’t a forecast and doesn’t replace medical, legal or financial advice. More in the Legal notice.

Who’s behind it

Pillars is a project by Violeta Osorio, in Argentina. For questions, or to report a mistake, write to violetaosorior@gmail.com.