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Why BaZi Calculators Give Different Results

By Data Saju · Published October 26, 2026

Two BaZi calculators can give different charts for the same birth because they make different choices on three settings: whether the clock is corrected to local solar time, whether the day changes at 11 PM or at midnight, and whether the year starts at Lichun or at Lunar New Year. Counting every minute of the day with our almanac engine, ignoring longitude changes the hour pillar for 2.5% of New York births (50% in Anchorage), the midnight day change moves the day pillar for 4.2% of births everywhere, and the year setting puts 7.4 days of the calendar a year (2%) into a different year on average.

Why do two BaZi calculators show different charts?

A BaZi chart turns a birth date and time into eight characters, but a few steps involve a convention rather than a fact. Calculators that agree on the stems and branches can still disagree on which date, hour or year a birth belongs to. These are the three that matter most, with how often each one changes the result.

Daylight saving time is a fourth source of differences for people born while clocks were moved forward; it has its own article, Born During Daylight Saving Time?. The percentages here are for standard time. They assume birth times are spread evenly through the day, and every minute of a day was run through the engine, so they are counts, not estimates.

Does the hour pillar use the clock or local solar time?

BaZi sets the hour by the Sun, so the clock has to be corrected for where you were born. Every time zone is built around one meridian (for example 75° W for Eastern time), and a city east or west of it runs ahead of or behind its clock by 4 minutes per degree. A calculator that skips this step reads the clock as is. Here is how often the two readings give a different hour pillar in winter (standard time), by U.S. city:

* Any of: clock as is, midnight day change, or both, compared with this site's default (solar time, 11 PM day change). ** Combined with the Lichun versus Lunar New Year gap (2% of days), treating the two as independent because the year depends only on the date. Winter dates only; daylight saving time is not included.

Denver sits almost exactly on its time zone's meridian, so the correction is under a minute and the hour pillar never changes. Anchorage is the opposite extreme: Alaska time is set to 135° W while the city is at about 149.9° W, so solar time runs 60 minutes behind the clock and exactly half of all hour pillars change. In New York, solar time is 4 minutes ahead of the clock, and only 2.5% change. If your birth time is near the start of a two-hour BaZi period on the clock (for example, just after 11:00 AM or 1:00 PM), local solar time is the first thing to check.

Does the day change at 11 PM or at midnight? The Rat hour

The Rat hour (子) runs from 11 PM to 1 AM, so it straddles midnight. Calculators split into two groups. One treats the whole Rat hour as the start of the next day, so the day pillar changes at 11 PM (solar time). The other lets the day change at midnight, so the late Rat hour (11 PM to midnight) still belongs to the first day and the early Rat hour (midnight to 1 AM) belongs to the next. This site uses the first. The hour pillar is the same either way; only the day pillar differs, and the day pillar holds your Day Master.

Worked example with the engine (a made-up birth): January 15, 2001, 11:30 PM in New York, which is 11:33 PM solar time.

The disputed window is exactly one hour of solar time, so 4.2% of births are affected. On the clock in New York in winter, that is 10:57 PM to 11:57 PM; in Denver it is 11:00 PM to midnight. If your birth time falls in that hour, find out which rule a calculator uses before you compare charts.

Is the year pillar based on Lichun or Lunar New Year?

The Chinese zodiac animal that most people know follows Lunar New Year. BaZi follows Lichun (Start of Spring), the solar term that falls around February 4, so the year pillar changes there. A calculator that uses Lunar New Year gives a different year pillar and animal for anyone born between the two dates. We compared both over the 200 years from 1900 to 2099, day by day:

On average the two disagree on 7.4 days a year (2% of birthdays), at most 16 days, and only 7 of the 200 years (1924, 1943, 1962, 2000, 2019, 2038, 2057) have no gap. In 2026, Lunar New Year was on February 17 but Lichun came on February 4, so babies born February 4 through February 16 are Horse (丙午) in BaZi but Snake (乙巳) on a Lunar New Year calendar. Dates use Korea time, so a Lichun that falls late in the evening in the U.S. may show a day later here. In rare years the Korean and Chinese calendars also place Lunar New Year a day apart. For more on the animal gap, see Korean saju vs. Chinese BaZi vs. Western astrology.

Check your own birth in four settings

Enter the time exactly as it appears on the birth certificate. Everything is calculated in your browser and nothing is sent anywhere. Daylight saving time is removed in every row; see the daylight saving article for details.

So which BaZi calculator is right?

• It is a convention, not an error. Each of these choices is widely used, so a difference does not mean one site made a mistake. What matters is knowing which choice a calculator makes.
• Check whether your birth time is in a gray zone. If your solar-time birth hour is not near a two-hour boundary, is not in the 11 PM to midnight hour, and is not between Lichun and Lunar New Year, most calculators will agree.
• Compare like with like. When two charts differ, look at which pillar changed. A different hour pillar points to solar time or daylight saving time, a different day pillar points to the Rat hour, and a different year pillar and zodiac animal point to Lichun versus Lunar New Year.
• If you do not know your birth time, use the three pillars (year, month, day) and leave out the hour.

Frequently asked questions

Why does my BaZi chart look different on another website? Calculators differ on local solar time, the Rat hour and whether the year starts at Lichun or Lunar New Year. In New York about 6.7% of birth times produce a different hour or day pillar under at least one alternative setting, and about 8.6% once the year setting is added.

What is the late Rat hour? It is the part of the Rat hour from 11 PM to midnight. Some calculators count it as the same day, others as the start of the next day, which changes the day pillar for 4.2% of births.

Should I use the clock or local solar time for BaZi? BaZi traditionally uses the Sun's position, so local solar time is the reading we use. Without it, the hour pillar changes for 2.5% of New York births and 50% of Anchorage births.

Does BaZi start the year at Lunar New Year? No. BaZi changes the year pillar at Lichun, around February 4. Lunar New Year sets the popular zodiac animal and differs from Lichun by 7.4 days a year on average.

How do I know which setting my chart needs? Use the checker above. If all four settings show the same hour and day pillars and Lichun and Lunar New Year give the same year, any calculator should match yours.

Counts come from this site's almanac engine: all 1,440 minutes of one winter day per U.S. city (standard time, birth times assumed evenly spread through the day), and every day of 1900–2099 at noon Korea time for the year setting. City longitudes are approximate.

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