The time on the clock and the solar time are different
The saju's hour pillar (時柱) is determined by the position of the sun. However, the clock we see uses a single standard time for the entire country, which misaligns with the sun's actual position.
Korea's standard time is based on 135° east longitude. Seoul's longitude is about 127°, so it is approximately 8° to the west, causing the sun to reach its zenith later — when it is noon by the clock, the sun in Seoul is still before its zenith. This difference is about 32 minutes.
The reason for asking where you were born
If the longitude is different, the adjustment amount will also differ. If you apply the Seoul-based adjustment to someone born overseas, the hour pillar will be significantly misaligned. Therefore, the input screen asks you to select your birthplace, and calculations are made based on that city's longitude and standard time. Currently, there are 56 places in the list.
Even within the same country, places with significantly different longitudes (such as the United States, Russia, Indonesia, etc.) have been divided into cities. 15° of longitude equals one hour pillar.
If you do not select, calculations will be made based on Seoul. Most births are domestic, so this is less prone to error, but if you were born overseas, please be sure to select.
Standard time has changed several times in the past
There is a reason why the adjustment cannot be calculated simply as "longitude difference ÷ 15° × 60 minutes." The standard time itself has varied over different eras.
| Period | What was different? |
|---|---|
| Before 1912 | There was no standard time (local mean time) |
| 1954 – 1961 | The standard time was UTC+8:30 |
| 1948 – 51 · 1955 – 60 · 1987 – 88 | Daylight saving time was implemented |
Saju-Link does not fix the standard meridian as a constant value, but calculates the actual standard time used at that moment based on the IANA time zone information of the birthplace. Daylight saving time and past standard times are automatically reflected.
Birth just after midnight also considers the date
Since the adjustment is -32 minutes, those born between 00:00 and 00:32 by the clock will be at 11 PM the previous day in true solar time. If only the time is adjusted back and the date remains the same, it will write the day pillar (日柱) as "11 PM the previous day."
Saju-Link will also adjust the date in this case. The character above the day pillar refers to the day stem (日干), which indicates myself, so if this is misaligned, almost all items in the interpretation will be misaligned.
You do not need to know the time
The birth time is optional. If you do not know it, calculations will be made without the hour pillar, and this fact will be displayed on the results screen. Since this means two out of the eight characters are missing, it will affect the assessment of the five elements' strength and weakness, so if you know it, it is more accurate to include it.
The year branch (the zodiac animal) is always the same regardless of the time — because we only look at the year branch.