True Solar Time Adjustment眞太陽時

The True Solar Time Adjustment, also called a birth time correction, shifts clock time to match where the sun stood at your birthplace. Korea Standard Time is set on 135 degrees east, but Seoul lies near 127 degrees. While that meridian is in use, the sun there peaks on average a little over 30 minutes later than the clock suggests. That moment also drifts through the year, by between about −14 and +16 minutes; this drift is the equation of time. Raw clock time can push a birth near a block edge into the neighbouring Hour Pillar.

• 眞real, genuine (Korean reading: jin)
• 太great, grand (Korean reading: tae)
• 陽the sun (Korean reading: yang)
• 時time, hour (Korean reading: si)

The sun's real time, read from its place in the sky.

Daylight saving dates lose one hour first. The longitude part is the birthplace longitude minus the standard meridian, times four minutes; the equation of time at birth is added. That sum is rounded once to the minute, with halves rounded up. For Seoul under the 135-degree meridian, 16 to 47 minutes come off by date. It touches only the Day and Hour Pillars, and options can switch it off.

Your calculation basis shows whether the adjustment was on, the minutes it moved, and its longitude and equation of time parts. For a Seoul birth from an odd hour on the dot to 15 to 46 minutes past, by date, the Hour Pillar depends on the adjustment. If another almanac disagrees, start here. That window assumes the 135-degree meridian without daylight saving. Births in Korean daylight saving summers within 1948–1951, 1955–1960 and 1987–1988 also lose an hour. That hour comes off even with the adjustment off.

A Seoul birth at 13:20 on 12 May 1990 loses 28 minutes, 32 for longitude less 4 for that day's equation of time. That gives 12:52 in the 午 (Wu) block, a 丙午 (Bing Wu) Hour Pillar. Unadjusted, 13:20 stays 未 (Wei): 丁未 (Ding Wei).

• A common idea

  After adjustment, the time matches the sun's position exactly.

  How we read it

  Even counting the equation of time, your birthplace is read as one reference point, such as a provincial capital, and the shift is rounded to the minute. A few minutes can separate this time from the sun's position at your actual birthplace.

• A common idea

  Everyone born in Korea has 32 minutes taken off.

  How we read it

  It varies by birthplace and date. Under the 135-degree meridian, Seoul's longitude part is 32 minutes, plus the equation of time. Busan's is 24; Seoul's is 2 from April 1908 to 1911 and March 1954 to August 1961.

Some calculators adjust for longitude only. Against them the gap is the equation of time, so a birth near a block edge can get a different Hour Pillar.