The difference between Saju and BaZi, with one chart read two ways

Saju (four pillars) and BaZi (eight characters) both describe the birth moment as four pairs of a Heavenly Stem and an Earthly Branch. Both take the Day Master from the day pillar, both set the month pillar by solar terms rather than by the calendar month, and both read Ten Gods, Five Elements, and luck cycles from the same structure.

So a Saju chart and a BaZi chart for the same birth moment should agree on the eight characters when the same inputs and the same conventions are used. When they do not, look first at the inputs and conventions in the sections below before concluding that one tradition is wrong.

A lunar date is defined by the moment of the new moon in a particular time zone. China uses UTC+8 and Korea uses UTC+9, so a new moon that falls close to midnight can land on different dates in the two calendars. The 2027 new year is a concrete case: the new moon falls at 15:56 UTC on February 6, which is 23:56 on February 6 in UTC+8 and 00:56 on February 7 in UTC+9. The Chinese-calendar new year is February 6, 2027, while the Korean calendar places lunar January 1 on February 7.

This only matters when someone gives a lunar birthday. A Saju tool built on the Korean calendar and a BaZi tool built on the Chinese calendar can convert the same lunar date to different solar dates in rare cases. If you know your solar birthday from an official record, use that and the question disappears. Hongsimdang converts lunar birthdays with the Korean calendar.

Both traditions divide the day into twelve two-hour branches, and both have long discussions about where the Zi hour begins around midnight. The practical difference is what time you feed into those branches. Some practitioners use the clock time on the birth record. Others convert it to local solar time using the birthplace longitude, so a birth in a city far from its time-zone meridian shifts by many minutes.

Korean Saju practice has paid close attention to this, partly because Korea itself changed standard time: the zone data show standard time at UTC+8:30 from March 1954 until August 1961, with daylight saving in some of those summers, and UTC+9 before and after. Hongsimdang applies the birthplace longitude to the hour pillar and uses the historical offset for the date, so a recorded time is interpreted under the rules in force on that day.

The terms map one to one. The characters are the same; the pronunciation and romanization differ, which is why English searches sometimes treat them as separate subjects. A reader moving between sources can use the list below as a translation key.

Readers in both traditions weigh seasonal balance, the strength of the Day Master, structure patterns, and luck cycles. Which of these gets the most attention depends on the school and the individual teacher, and generalizations such as “Korean readers do this, Chinese readers do that” break down quickly when you compare actual practitioners.

The more useful comparison is between a reading that names its method and one that does not. Ask which calendar, which hour convention, and which birth location rule a reading used. A reading that can state those can be checked, and a reading that cannot is hard to compare with anything else.