A calendar does not change the moment you were born. It changes how that moment is written down.
A solar date and its correctly converted lunar date point to the same day. They are not competing birthdays and they do not create two different Saju charts. YourSaju first resolves the calendar notation, then calculates one verified Manse-ryeok birth record from the converted date, local time, and birthplace.
If a Korean lunar birth date asks “regular or leap month?”, open the two terms below before choosing.
REGULAR MONTH평달+
A regular month is the ordinary numbered month in that lunar year. Choose it when the family record does not identify the birth month as a leap month.
Most lunar birth records use a regular month.LEAP MONTH윤달+
A leap month is an extra lunar month inserted in some years to keep lunar months aligned with the solar seasons. It repeats a month number, so “regular fourth month” and “leap fourth month” are different date records.
Choose leap month only when the original birth record explicitly says 윤달.NOT SURE? Do not guess. Confirm the original family or official record before calculating the chart.
The Solar Calendar
The modern solar calendar keeps the year aligned with the seasonal journey of the sun.
Most international birth records use the Gregorian solar calendar. In Saju, however, entering a Gregorian date does not mean every pillar changes on an ordinary civil-calendar boundary. The Year and Month Pillars follow solar-term boundaries used by the Manse-ryeok calculation.
The bronze angbuilgu in this room is a Joseon hemispherical sundial. Historically it read the sun’s shadow to show time and seasonal divisions. Here it represents observation and measured solar movement; it is not the device performing your digital calculation.
The Korean Lunar Calendar
The calendar commonly called “lunar” in Korea is more precisely lunisolar.
Its months follow the changing lunar cycle, while its year must remain connected to the solar seasons. Because lunar months do not add up evenly to one solar year, an intercalary—or leap—month is inserted when required. That is why a lunar birth record must also say whether the month was a regular month or a leap month.
The water-clock vessel evokes Joseon timekeeping through the night. It measured passing time; it did not calculate the lunar calendar. The moon, astronomical record, and flowing water work here as visual guides, while the page keeps their historical roles separate.
How YourSaju Uses Your Date
- 1Preserve the original entry.
Your selected calendar, date, and lunar leap-month status remain part of the calculation record.
- 2Resolve one solar date.
A lunar entry is converted before the Four Pillars are calculated. A solar entry already supplies that civil date.
- 3Place the moment in its birthplace.
Local birth time, historical time zone, city longitude, and the selected day-boundary rule determine the calculation context.
- 4Calculate—never guess.
If birth time is unknown, the Hour Pillar and Daewoon start remain withheld instead of being invented.
The calendar is the doorway, not the interpretation.
The Manse-ryeok calculation resolves the birth record first. Interpretive language begins only after the chart exists.Calendar conversion is reviewed against established Korean public standards. Historical instrument notes use Korean public heritage and museum records.