What is true solar time in saju?

True solar time is the time set by the sun's actual position at your birthplace, rather than the standard clock time of your time zone. Saju's hour pillar is meant to follow the sun, but the time on your birth certificate is standard clock time tied to a time-zone meridian. Because your birthplace usually sits east or west of that meridian, true solar time differs from clock time by a few minutes to over half an hour, which is what the correction adjusts for.

Why does longitude change my hour pillar?

Clocks within a time zone all read the same, but the sun does not rise at the same moment across the whole zone. Each degree of longitude away from your zone's central meridian shifts true solar time by about four minutes. If your birthplace is far from that meridian, the accumulated shift can move your birth across a two-hour earthly-branch boundary and change your hour pillar to the neighbouring block.

Does daylight saving time affect my saju chart?

Yes, and it is a common hidden error. If you were born while daylight saving time was in effect, the recorded clock time is typically one hour ahead of standard time. Ignoring that hour can push your birth into the wrong two-hour block and give you the wrong hour pillar entirely. Whether your birthplace and date actually observed daylight saving has to be checked, because rules changed over the years and by region.

Do I need to calculate the correction myself?

No. A good calculator applies longitude and, where relevant, daylight-saving adjustments for you once it knows your birthplace and the standard clock time. You enter the time as it was recorded, mark daylight saving if it applied, and the tool converts it to true solar time before placing your hour pillar. You should not try to shift the minutes by hand.

Who most needs the true-solar-time correction?

Three groups: people born near a two-hour block boundary, people born far from their time zone's central meridian, and people born during daylight saving time. If any of these apply, the correction can decide which hour pillar is truly yours. If you were born comfortably inside a block and far from any boundary, the correction usually leaves your hour pillar unchanged.

Cheonmyeongdang › True Solar Time Correction

Saju True Solar Time — Why Your Clock Birth Time Can Be Wrong

Q: How much can the correction change my reading?

When the correction moves you across a two-hour block, the whole hour pillar changes — its stem and branch both shift. That can alter how strong or weak your Day Master reads, change which ten-god sits in the hour position, and adjust themes traditionally linked to the hour pillar. For most people the correction is small and harmless, but for anyone born near a block boundary it can change the chart meaningfully.

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The time on your birth certificate is clock time — not true solar time. Saju's hour pillar follows the sun, and the gap between the clock and the sun can be large enough to push you into the wrong two-hour block. Two things cause that gap: longitude (your distance from your time zone's meridian) and daylight saving time. This guide explains both in plain English, shows when the correction actually changes your chart, and lets you get an accurate four pillars reading free.

Clock time is a convenience, not the sun

Everyone in a time zone shares one clock, but the sun does not reach its high point at the same moment across the whole zone. Standard time is tied to a single central meridian; your birthplace usually sits east or west of it. That offset — plus daylight saving if it was in effect — is the difference between the time printed on your records and the true solar time saju actually wants for the hour pillar.

The hour pillar runs in two-hour blocks. A correction only matters when it moves your birth across a block boundary. Deep inside a block, a few minutes change nothing; near the edge, those same minutes can flip the entire hour pillar.

The two corrections, in plain English

Correction	What it is	Size
Longitude	Your distance from the time zone's central meridian	About 4 minutes per degree — can add up to half an hour or more.
Daylight saving	The clock was pushed ahead while DST was in effect	Usually one hour — large enough to jump a whole block.

Both pull in one direction: turning your recorded clock time into the true solar time of your birthplace. A calculator that knows your birthplace and whether DST applied does this for you; you should never nudge the minutes by hand.

What changes when the hour pillar flips

If the correction carries you into the neighbouring two-hour block, the hour pillar's stem and branch both change. That can shift how strong or weak your Day Master reads, change which ten-god sits in the hour position, and adjust themes traditionally tied to the hour pillar. A chart built on uncorrected clock time can look complete and still place this pillar one step off.

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Do you actually need the correction?

For many people the correction is small and the hour pillar does not move. It matters most for three groups:

Born near a block boundary — within roughly half an hour of a two-hour edge, where any shift can tip you over.
Born far from your meridian — the longitude offset is largest at the eastern and western edges of a time zone.
Born during daylight saving — a recorded hour that is one ahead of standard time can quietly land you in the wrong block.

If none of these apply, your uncorrected time and your true solar time usually point at the same hour pillar — but it is still worth letting the tool confirm it.

How to get an accurate hour pillar

STEP 1

Enter your birth time exactly as it was recorded — do not pre-adjust the minutes yourself.

STEP 2

Set your birthplace so the calculator can apply the longitude correction for that location.

STEP 3

Mark daylight saving if it was in effect on your birth date and place, so the hour is read against standard time.

STEP 4

Let the tool convert to true solar time and place your hour pillar in the correct two-hour block.

What this guide will not promise

True solar time makes your hour pillar accurate; it does not turn saju into a guarantee of any outcome. Saju is a centuries-old framework for reflection and self-understanding. The point of the correction is honesty: reading the hour pillar that genuinely matches the sun at your birth, rather than one placed by an uncorrected clock.

Common questions

I do not know if daylight saving applied — what now?

Use your birthplace and date to check whether DST was in effect there at the time, since rules changed over the years and by region. A calculator with that history applies it for you; when in doubt, note both possibilities and see whether they land in the same block.

What if I do not know my birth time at all?

True solar time only helps once you have a clock time to correct. If you have no time, that is a different situation — see the guide to saju without a birth time.

Does the calendar I use affect this too?

Yes, separately. The calendar fixes the day your pillars sit on; true solar time fixes the hour. If you are unsure whether to enter a lunar or solar date, read lunar or solar birth date.

Where can I see my corrected chart for free?

Right here. The free Cheonmyeongdang calculator applies longitude and daylight-saving corrections once it knows your birthplace and recorded time, then shows your Day Master and Five Elements in plain English.