BaZi Calculator: Your Four Pillars of Destiny

Work out your four pillars

Each pillar is one Heavenly Stem paired with one Earthly Branch. The ten stems carry the five elements in a yang and yin form — Yang Wood, Yin Wood, Yang Fire, and so on. The twelve branches are the same twelve signs that carry the zodiac animals, which is why the year branch of the sample 15 June 1990 chart is Wǔ, the Horse. The stem and branch advance together in a repeating sixty-step cycle, so a full stem-and-branch pair returns only once every sixty years. That cycle is set out in more detail on our page about the 60-year Chinese zodiac cycle, and the naming logic behind the pairs is covered under Heavenly Stems and Earthly Branches.

Under the Lìchūn convention, the year turns before Chinese New Year

This is where most online charts and most casual assumptions part company. Two different conventions for starting a new year are both in use. Ordinary zodiac-year lookup — the kind that tells you which animal a given year belongs to — changes on the first day of the lunar year. Many BaZi systems, including this calculator, change at Lìchūn, the solar term called Start of Spring, which falls when the sun reaches an apparent ecliptic longitude of 315°. In practice that lands on 3, 4 or 5 February.

The gap matters more than it sounds, because Chinese New Year can fall anywhere from late January to late February. In 2026, Lìchūn arrives on 4 February and Chinese New Year not until 17 February — leaving a stretch of thirteen days where the two disagree. Someone born on 10 February 2026 is still in the lunar Year of the Snake, but under the Lìchūn convention used here their BaZi year pillar has already turned to the Fire Horse year. Our wider discussion of that trap is on the page for January and February zodiac birthdays.

The month pillar follows the solar terms, not the lunar months

A second assumption worth dropping: the BaZi month is not the lunar month. The traditional calendar divides the solar year into twenty-four solar terms, and those alternate between twelve jié (節, the “nodes”) and twelve zhōngqì (中氣, the “middle breaths”). Only the twelve jié start a BaZi month. The twelve middle breaths — including familiar ones like the equinoxes and solstices — play no part in setting the month pillar at all.

The stem of the month is then derived from the stem of the year by a fixed rule traditionally memorised as the wǔ hǔ dùn, the Five Tigers method: a Jiǎ or Jǐ year opens its Tiger month with Bǐng, an Yǐ or Gēng year with Wù, a Bǐng or Xīn year with Gēng, a Dīng or Rén year with Rén, and a Wù or Guǐ year with Jiǎ. From there the stems simply run on in order. The hour stem is produced the same way from the day stem, under the parallel wǔ shǔ dùn or Five Rats method.

The 23:00 problem, and why we show you two answers

The Zǐ hour runs from 23:00 to 01:00, which means it straddles midnight. Traditions disagree about what that does to the day pillar, and the disagreement is old rather than modern — it is already visible in Ming-dynasty compendia.

Only births between 23:00 and 23:59 are affected — roughly one hour in twenty-four. For those births the calculator prints both readings side by side rather than picking one silently, because the difference is a difference of school, not a calculation error, and no amount of arithmetic will settle it.

Two separate questions about time

Charts differ between sites more often over time handling than over anything else, and the confusion usually comes from running two distinct questions together.

The first is when the birth actually happened. That is a single moment, and it is the same moment whichever clock records it. Because the year and month pillars are set by comparing that moment against solar term instants, they need your birth converted to a common reference before anything is compared. This is why the form asks for the UTC offset in force at your birthplace: a birth recorded as 20:00 in New York on 3 February 2026 is already past Lìchūn, even though Lìchūn falls on 4 February in the reference the table uses. Daylight saving belongs here, as part of the offset — a birth written as 03:30 daylight time and one written as 02:30 standard time are the same instant described twice, so switching between the two descriptions does not move the birth relative to Lìchūn.

The second is which local clock the hour pillar should follow. That is a question of school rather than of astronomy. This calculator reads the hour from the local clock time you enter. Some BaZi schools instead adjust that time toward true solar time at the birthplace, which introduces two further differences:

Neither is applied here, and that is a stated choice rather than an oversight — the true-solar-time adjustment is one tradition among several, and applying it silently would hide a decision the reader ought to be making. Where the recorded time sits close enough to a boundary for any of this to matter, the result panel says so.

Where the dates come from

Solar term instants on this page are computed from the VSOP87 planetary theory, taking the sun’s apparent geocentric longitude — that is, including aberration and nutation — and solving for the moment it crosses each multiple of 15°. The instants are stored to the second, expressed in UTC+8, and frozen into a fixed table rather than recomputed in your browser, so the same birth data always returns the same chart. Your birth moment is converted into that same reference before the two are compared, which is what the UTC offset field is for.

The table was checked term by term against the Hong Kong Observatory’s published Gregorian–Lunar calendar for 1901 to 2100. Of 4,800 solar term dates, 4,794 match. The six that differ were re-checked against JPL Horizons, whose DE441 ephemeris supports the dates used here; those six are retained as fixed regression cases rather than adjusted to force agreement. Our general approach to calculation and sourcing is described under how we calculate.

Day pillars run as an unbroken sixty-day cycle that ignores the calendar entirely — no leap years, no lunar months, no solar terms. The anchor used here is 7 January 2000 as a Jiǎ-Zǐ day, cross-checked against independent almanac sources.

Dates entered into the calculator are read as Gregorian. That matters for older records: if a birth was written down under the Julian or Old Style calendar — Russia kept it until February 1918, Greece until 1923 — or given as a traditional lunar date, it needs converting first, or the chart comes out roughly a fortnight adrift. The offset field has a similar caveat. It asks for the offset actually in force at the birthplace on that date rather than the one in force there now, and for births much before 1970 the historical offset can itself be uncertain; where that uncertainty could change the result, the panel above says so.

Questions people ask

Keep reading

Got your pillars — want them read, not just calculated?

This tool produces calendar arithmetic: the exact stem-branch names for a moment in time. Turning those names into a written interpretation, or comparing two charts, is a separate step: