Late and Early Zi Hour夜子時·朝子時

The late and early split arises because the Zi hour, from 23:00 to 01:00, straddles the line between two days. As the first of the twelve two-hour blocks it can open a new day, yet the calendar date changes only at midnight, so the 23:00 hour can also count as today. Hence the split: the 23:00 hour becomes the late Zi hour, at night, and the hour after midnight the early Zi hour. Views differ even on when this split entered chart reading, and schools still disagree on which way to go.

• 夜night (Korean reading: ya)
• 朝morning (Korean reading: jo)
• 子child (Korean reading: ja)
• 時time of day (Korean reading: si)

Night and morning Zi hours: the hour on each side of midnight.

By default this service uses a single Zi hour. An adjusted time in the 23:00 hour moves the Day Pillar to the next day, and the Hour Pillar stem follows that day's Day Master. The split option keeps the same day's Day Pillar for the 23:00 hour and takes only the Hour Pillar stem from the next day, keeping the sixty-pair Hour Pillar sequence unbroken. From midnight to just before 01:00, both give the new day's Zi hour.

Born between 23:00 and midnight? Start by checking which method the calculation basis in your results names. The two methods put the Day Pillar a day apart, so the Day Master changes and every Ten Gods and Twelve Life Stages entry with it. If another almanac defaults to the split, switch the option to compare. An unknown birth hour means no Hour Pillar, so the choice has no effect.

A Seoul birth at 23:40 on 12 May 1990 adjusts to 23:12. Under a single Zi hour that gives a 戊寅 (Wu Yin) Day Pillar and 壬子 (Ren Zi) Hour Pillar; the split gives 丁丑 (Ding Chou) and 壬子. A 23:10 birth that day adjusts to 22:42, the 亥 (Hai) hour.

• A common idea

  The split is right and the single Zi hour wrong, or vice versa.

  How we read it

  Both are in use, and schools disagree on which is right. This service defaults to the single Zi hour and records the method in your results.

• A common idea

  Past 23:00 on the clock, a birth is in the Zi hour regardless.

  How we read it

  Under the 135-degree east meridian, a Seoul birth loses 16 to 47 minutes by date, so a little after 23:00 can still be the Pig hour. On 12 May 1990, that holds to 23:27.

If the 23:00 hour kept its own day's Day Pillar and took the Hour Pillar stem from that day too, the stem would differ even from the split option here. This service uses the next day's Day Master to keep the Hour Pillar sequence continuous.