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When our result differs from a traditional almanac — true solar time, daylight saving and the midnight boundary.
Device
Clocks follow a standard meridian; the sun follows yours. Seoul sits near 127°E while Korean standard time is set at 135°E, so solar noon arrives about half an hour after the clock says so. Choosing your birth city corrects for this automatically.
1
The correction combines the longitude offset with the equation of time — the drift between the real sun and the average one.
2
If the corrected time crosses a two-hour boundary, the hour pillar shifts. This is the most common reason a chart differs from an almanac.
3
You can turn the correction off during onboarding.
Korea's standard time and daylight saving rules changed several times. We calculate with whatever was actually in force on your birth date.
1
From 21 March 1954 to 9 August 1961 Korea ran on UTC+8:30.
2
Daylight saving was in force in 1948–51, 1955–60 and 1987–88.
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If you were born in one of those windows, clock time and solar time diverge by up to an hour.
The Rat hour spans 23:00 to 01:00, and schools disagree on whether the hours before midnight belong to that day or the next. We apply a default, but if you were born in that window both readings are worth comparing.
My chart differs from an almanac app.
Usually true solar time. Almanacs that skip the correction land on a different hour pillar near the boundaries. Neither is wrong — the basis differs.
What happens if I turn the correction off?
We use the clock time as entered. If you want to match a traditional almanac, that may suit you better.
My birth city isn't listed.
Type it anyway — the chart still builds. Without coordinates, though, no true solar correction is applied.
Worth knowing
· Changing the basis recalculates your chart and regenerates existing readings against it.
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