Why does my month pillar change when I pick a different city?

It should not, unless your birth falls within hours of a solar term: the year and month pillars are compared as instants, so only the time zone conversion matters. The day and hour pillars do change with longitude, because they use true solar time.

What is the Day Master?

The heavenly stem of your day pillar. In BaZi it represents the person; the other seven characters are read as resources, output, wealth, pressure or peers relative to it.

My birth time is unknown. What can I do?

Enter 12:00 and ignore the hour pillar; the year, month and day pillars stay valid. The hour pillar is the only one that needs the time.

Is this the same as the zodiac calculator?

The zodiac calculator gives the year animal under both boundaries; this tool gives the full four-pillar chart. Both use the same engine and the same Lichun instants.

BaZi Four Pillars Calculator

BaZi (八字, "eight characters") writes your birth moment as four stem-branch pairs — year, month, day and hour. The chart is only as good as the time it is computed from, which is why this calculator asks for the birthplace: the hour pillar is read from true solar time, not clock time, and the year and month pillars change at the exact instants of the solar terms.

The result is the raw chart plus the two facts every reading starts from — the Day Master (the stem of the day pillar, which stands for you) and how the five elements are distributed across the eight characters. Interpretation of strength, useful elements and the ten gods is the part a report does.

Birth details (clock time at the birthplace)YearMonthDayHour (0–23)MinuteBirthplace (for time zone and true solar time)Late Zi hour (23:00–24:00)Only matters if you were born between 23:00 and midnight true solar time: the two schools disagree on whether the day pillar changes at 23:00 or at midnight.

Pillar	Stem-branch	Heavenly stem	Earthly branch
Year 年柱	辛未	辛 · Yin Metal	未 · Earth · Goat
Month 月柱	乙未	乙 · Yin Wood	未 · Earth · Goat
Day 日柱	丙戌	丙 · Yang Fire	戌 · Earth · Dog
Hour 时柱	癸巳	癸 · Yin Water	巳 · Fire · Snake

Day Master (日主)

丙 — Yang Fire

The Day Master is the stem of your day pillar: the element that stands for you in the chart. Every other element is read relative to it.

Five-element count across the eight characters (stems and branches counted once each; hidden stems not weighted).
Wood	Fire	Earth	Metal	Water
1	2	3	1	1

Zodiac	Goat by Lichun
True solar time	10:58 on 1991-07-15 — clock time −4h UTC, longitude correction -56 min, equation of time -5.8 min (New York, United States)
Late Zi rule	Day changes at 23:00 (default)
2027 (丁未) and your chart	Your year branch 未 vs the Tai Sui 未: same. The annual stem 丁 (Fire) is the same element as your Day Master (peer). See the Goat in 2027 →

How this calculator works

Year and month pillars: the birth instant is converted to UTC and compared with the astronomical solar terms (Lichun for the year, the twelve "Jie" terms for the months). Day and hour pillars: the clock time is corrected by longitude (4 minutes per degree from the time zone's standard meridian) and by the equation of time, then the hour branch is read from the corrected time.

Late Zi hour: between 23:00 and midnight true solar time, one school changes the day pillar at 23:00 (the default here, used by tyme4ts and most calculators) and another keeps the day pillar until midnight. Both schools take the hour stem from the next day's stem; the switch above lets you see the other reading.

The five-element count is a simple tally of the eight characters. Hidden stems inside the branches and seasonal strength are not weighted here — that is where interpretation begins.

Frequently asked questions

Why does my month pillar change when I pick a different city?: It should not, unless your birth falls within hours of a solar term: the year and month pillars are compared as instants, so only the time zone conversion matters. The day and hour pillars do change with longitude, because they use true solar time.
What is the Day Master?: The heavenly stem of your day pillar. In BaZi it represents the person; the other seven characters are read as resources, output, wealth, pressure or peers relative to it.
My birth time is unknown. What can I do?: Enter 12:00 and ignore the hour pillar; the year, month and day pillars stay valid. The hour pillar is the only one that needs the time.
Is this the same as the zodiac calculator?: The zodiac calculator gives the year animal under both boundaries; this tool gives the full four-pillar chart. Both use the same engine and the same Lichun instants.