How this calculator works

BaZi (八字, "eight characters") maps a birth moment onto four pairs of Heavenly Stems and Earthly Branches: one pair each for the year, month, day and hour. Everything downstream of the chart depends on drawing those eight characters correctly, and two boundaries cause most errors.

The year begins at Lichun, not January 1

The BaZi year changes at Lichun (立春), the solar term when the sun reaches celestial longitude 315°, usually February 3–5. Cinnabar computes the actual astronomical instant of each term (to within a few minutes) rather than reading a fixed date from a table, then compares it against your birth instant in your birth timezone. Months work the same way: each of the twelve BaZi months opens at a solar term, not on the first of a calendar month.

Days ride a sixty-day cycle

The day pillar follows an unbroken sixty-day stem-branch cycle that has run for millennia; this page anchors it arithmetically rather than by lookup, so any date from 1900 to 2099 resolves exactly. The day belongs to your local civil date, and the hour pillar is derived from the day stem by the classical Five Rats method (五鼠遁).

Reading the chart

• Day Master (日主) — the day pillar's stem, highlighted in red. In modern BaZi it stands for you; every other character is read in relation to it.
• Ten Gods (十神) — the small caption over each stem names its relation to the Day Master: what supports you, what you command, what commands you.
• Hidden stems (藏干) — each branch stores one to three stems beneath the surface; they matter in a full reading and are listed under each pillar.

Honest limits

• Born within an hour or two of a solar-term instant? The month or year pillar can genuinely flip; the page warns you when your birth falls that close to a boundary.
• The hour pillar assumes clock time. Purists adjust to true solar time (position in your timezone plus the equation of time), which can shift births near a two-hour boundary; if you were born on the edge of an hour branch, read both.
• Historical daylight-saving time is not auto-corrected; if DST applied at your birth, subtract one hour first.

A chart is a description of tendencies in a thousand-year-old symbolic language, not a verdict. Nothing here is medical, legal or financial advice.