Four pillars (八字) from your birth date, time, and place. Computed deterministically with true solar time correction, the way a careful practitioner would, never guessed by an AI. Free, no sign-up, and nothing you enter leaves this page.
The chart is the map. The conversation is the territory. In the app, this chart opens a contemplative reading you can question, one thread at a time, plus a daily lot and couple compatibility.
Continue in the appA BaZi chart is easy to get subtly wrong. The year turns at the Start of Spring solar term, not on January 1. Each month turns at the exact minute of a solar term, not on the 1st. The hour follows where the sun actually was over your birthplace, not the clock on the wall. This calculator leaves all of it to a deterministic astronomical engine (solar terms to the minute, true solar time from your birthplace's longitude), the same engine inside the Reckoned Yet? app. The math is never left to a language model.
Your birth details are processed entirely in your browser. They are not sent to a server, not stored, and not logged.
At 立春 (Start of Spring), the moment the sun reaches 315° of ecliptic longitude, which falls on February 3, 4 or 5. It is not January 1 and not the Lunar New Year. Someone born in late January or early February may still belong to the previous year's pillar. 立春 also begins the first month, so the month pillar changes at the same moment.
Each BaZi month begins at one of the twelve 節 (jié) solar terms, which fall around the 4th to the 8th of each Gregorian month. Solar terms are set by the sun's position, so each change happens at a particular minute. This calculator takes those minutes from a table computed for every year from 1900 to 2100, and says so in the result when a birth falls close to one.
The twelve two-hour blocks of the hour pillar follow the sun, not the clock. To find the sun time of a birth, the calculator removes daylight saving time if it was in force that day in your city, adds 4 minutes for every degree your birthplace lies east of its time zone's reference meridian (or subtracts them if it lies west), and applies the equation of time, the seasonal gap of up to about 16 minutes between sun time and clock time. Together these can shift a birth by tens of minutes, enough to change the hour pillar.
Sources: Hong Kong Observatory, the 24 solar terms; Wikipedia, Equation of time; NOAA, solar calculation details.