Eight FatesOpen the calculator

Calculation methodology · reviewed July 28, 2026

How our BaZi
calculator works

A Four Pillars result can change at a solar-term instant, at midnight, or when local clock time crosses an Hour Pillar boundary after birthplace correction. This page states the calculation order and the conventions Eight Fates uses.

  1. 01

    Civil birth time

    Date, local clock time, and birthplace

  2. 02

    Solar correction

    Time zone, DST, longitude, and equation of time

  3. 03

    Jie Qi boundary

    Time-specific solar-term month and year boundary

  4. 04

    Four Pillars

    Year, month, day, and hour Gan-Zhi pairs

The calculation

Four decisions, in order

1. Read local time

We begin with the recorded local date and clock time. When a supported city is selected, its IANA time-zone history supplies the UTC offset in force on that date, including historical daylight-saving rules.

A repeated clock time during an autumn DST rollback is ambiguous without an additional standard/daylight designation. In that rare case, the earlier occurrence is used.

2. Find solar time

Exact-time entries are converted to apparent solar time using the birthplace longitude, the date-specific UTC offset, and the seasonal equation of time. The correction is rounded to the nearest minute.

correction = equation of time + 4 × longitude − UTC offset minutes

If the corrected time passes midnight, the corrected calendar date moves with it. That rollover matters because it can change the Day Pillar, not only the Hour Pillar.

3. Resolve Jie Qi

The BaZi year and month use time-specific Jie Qi boundaries from thelunar-typescript calendar library. Li Chun is therefore evaluated at its transition time for that year, not as a fixed all-day February 4 rule.

4. Build the chart

The resulting calendar instant produces the Year, Month, Day, and Hour Gan-Zhi pairs. Eight Fates uses the sect 2 convention: the Day Pillar changes at civil midnight, while 23:00 remains the first half of the Zi Hour.

Element balance counts the visible stems and branches plus their hidden stems. Interpretation is applied only after the underlying Four Pillars chart exists.

Boundary checks

Why two calculators can disagree

A different answer is often a convention difference, not a different interpretation of the same chart. Compare these inputs and boundaries first.

Birth date
What it changesSets the calendar day and is the starting point for the Year, Month, and Day Pillars.
Most sensitive whenDates close to Li Chun or another monthly Jie Qi.
Exact birth time
What it changesSets the two-hour branch and can resolve a solar-term transition on the same date.
Most sensitive whenTimes near midnight, a two-hour boundary, or a Jie Qi instant.
Birthplace
What it changesChanges civil clock time into apparent solar time before the chart is generated.
Most sensitive whenPlaces far from the time-zone meridian and dates observed under daylight saving.

Reference

Solar-time formula

The equation-of-time approximation follows the published NOAA Solar Calculator equations. It accounts for the seasonal difference between mean clock time and the apparent motion of the sun.

Read NOAA's equations

Known limits

What the form cannot know

  • Solar correction is applied only when an exact time and a supported city are provided. Rough two-hour periods remain approximate.
  • Birth records during a repeated DST hour may need an extra standard/daylight-time note that the current form does not collect.
  • The public calculator accepts birth dates from 1900 through 2100. Interpretive text is a cultural and reflective framework, not guaranteed prediction or professional advice.

Use the same method

Calculate your Four Pillars

The chart, Day Master, and element balance are visible before any purchase. No account or email is required.

Check true solar time →Open the free calculator