Korean standard time history matters for saju because your hour pillar depends on the clock. Korea’s official time has switched between UTC+8:30 and UTC+9 more than once, and daylight saving time (DST) came and went in several years, including 1987 and 1988. If you were born in one of those windows, the time on your record may need a small adjustment before it becomes a saju hour.
On top of that, many practitioners apply true solar time, because Seoul sits about 32 minutes west of the meridian that Korea’s clocks follow.
None of this changes who you are. It just makes sure the chart is drawn from the right moment.
Why a few minutes can matter
Saju divides the day into twelve double-hours, each linked to an earthly branch. In the standard table, 子 ja (Rat) runs 23:00–01:00, 丑 chuk (Ox) 01:00–03:00, and so on through 亥 hae (Pig) at 21:00–23:00.
If you were born in the middle of a double-hour, a 30-minute shift changes nothing. If you were born near an edge, it can move you into the next branch, which changes your hour pillar. Near 23:00, some schools also treat the start of the Rat hour as the start of a new day, so the day pillar can be affected too.
That is why saju readers ask for the place of birth as well as the time.
A short history of Korean clock time
Here is the timeline, based on public records of Korean time and the international time zone database used by computers.
| Period | Official offset | Notes |
|---|---|---|
| From 1908 | UTC+8:30 | Standard time adopted under the Korean Empire |
| From 1912 | UTC+9 | Changed to match Japan Standard Time |
| 1948–1951 | UTC+9, with summer DST | DST in several summers |
| 1954 to 1961 | UTC+8:30 | Standard time moved back to UTC+8:30 (March 21, 1954 to August 9, 1961) |
| 1955–1960 | UTC+8:30, with summer DST | Summer clocks one hour ahead, at UTC+9:30 |
| From August 10, 1961 | UTC+9 | Korea Standard Time as used today |
| 1987 and 1988 | UTC+9, with summer DST | Clocks ran at UTC+10 from about mid-May to mid-October |
The 1988 daylight saving period is the best known. It ran from May 8 to October 9, 1988, around the Seoul Summer Olympics, so that daytime events could air live during prime time in the United States. South Korea does not use DST today.
What “true solar time” means
Clock time is a convention. Korea Standard Time (UTC+9) is set by the 135°E meridian. Seoul lies around 127°E. The sun takes about four minutes to cross each degree of longitude, so solar noon in Seoul comes roughly 32 minutes after clock noon.
Many saju practitioners adjust for this, reasoning that the double-hours were originally defined by the sun. Others use clock time as recorded. Both approaches exist, and a good tool tells you which one it is using.
An interesting side note: during the UTC+8:30 era of 1954 to 1961, Korea’s clocks followed the 127.5°E meridian, which runs very close to Seoul. So for Seoul births in those years, clock time and solar time were only about two minutes apart outside the DST months.
Three worked examples
1. A summer 1987 birth in Seoul at 23:20. DST was in effect, so the clock read one hour ahead. Standard time was 22:20. With true solar time, subtract about 32 minutes: roughly 21:48. That is the 亥 hae (Pig) hour. Read straight off the clock with no corrections, the same birth would land in the 子 ja (Rat) hour, and some schools would even move it to the next day.
2. A January 1958 birth in Seoul at 07:10. It was winter, so no DST, but the official offset was UTC+8:30. Seoul’s solar time was almost the same, around 07:08: the 辰 jin (Dragon) hour. If a tool wrongly assumed UTC+9 and subtracted 32 minutes, it would get 06:38 and land in the 卯 myo (Rabbit) hour instead.
3. An October 2000 birth in Seoul at 14:10. No DST, standard UTC+9. With true solar time, about 13:38: still 未 mi (Goat), 13:00–15:00. Most births don’t need any drama. The corrections matter only near the edges.
How to check your own birth time
- Find the recorded time. Family records, a hospital note or a parent’s memory. Write down how exact it is (“around lunch” is different from “12:47”).
- Write down the city. Busan sits further east than Seoul, and Incheon a little further west, so their solar-time corrections differ slightly.
- Check the date against the table. Before August 1961? During a DST summer? In 1987 or 1988 between mid-May and mid-October?
- Know your tool’s settings. A good manseryeok (만세력 萬歲曆, saju almanac) handles historical offsets and lets you see whether true solar time is applied.
- Note the rat-hour rule. Some schools split the 子 hour into early and late halves (야자시 yajasi and 조자시 jojasi). If you were born between 23:00 and 01:00, compare both versions.
If you were born abroad, the same logic applies. Use the local clock time, the local time zone rules for that year, and the longitude of the place.
If you don’t know your birth time
That’s very common, and it’s fine. Without an hour, you still have three pillars, six of the eight characters, including your day master (일간 ilgan), the heart of the chart. Many readings work well on that basis. The hour pillar is traditionally linked to later life, plans and inner wishes, so you’ll simply read those themes more loosely.
What we’d suggest avoiding: guessing a birth time just to get a chart you like. A reading built on an invented hour tells you more about the guess than about you.
FAQ
Did South Korea use daylight saving time in 1987 and 1988?
Yes. Clocks moved one hour ahead, to UTC+10, from about mid-May to mid-October in both years. In 1988 the period ran from May 8 to October 9, around the Seoul Olympics. Korea also used DST in several summers between 1948 and 1960. For a saju chart, subtract that hour to get standard time first.
Why was Korea on UTC+8:30?
Korea first adopted UTC+8:30 in 1908, then changed to UTC+9 in 1912. In 1954 the South Korean government returned to UTC+8:30, and in 1961 it switched back to UTC+9. For births between 1954 and 1961, a saju tool should use UTC+8:30, plus DST where it applied.
Should I use true solar time for my saju?
It depends on the school you follow. Many practitioners adjust for longitude, which for Seoul means about 32 minutes earlier than Korea Standard Time. Others read clock time as recorded. If your birth time is near a double-hour boundary, look at both versions and see which description resonates more. Most births aren’t affected at all.
What if my birth time is only approximate?
Use the best estimate you have and note the uncertainty. If the window sits comfortably inside one double-hour, you’re fine. If it crosses a boundary, compare the two possible hour pillars, or skip the hour and read a three-pillar chart. Your day master and the rest of the chart stay the same either way.
Try it with the Moon Rabbit
The free pro chart shows your full four pillars, so you can compare hour pillars if your time sits near an edge. For a quick friendly overview, start with a free saju card. Without sign-in, your birth details stay in your browser.
Saju is a cultural tradition, not a science. SajuBunny readings are for fun and self-reflection, not professional advice.