The Twelve Double-Hours: Which Day Do You Belong to If Born After 11 PM?
BaZi hour pillars follow the twelve traditional double-hours, two clock-hours each:
| Branch | Clock time | Branch | Clock time |
|---|---|---|---|
| Zi 子 | 23:00–01:00 | Wu 午 | 11:00–13:00 |
| Chou 丑 | 01:00–03:00 | Wei 未 | 13:00–15:00 |
| Yin 寅 | 03:00–05:00 | Shen 申 | 15:00–17:00 |
| Mao 卯 | 05:00–07:00 | You 酉 | 17:00–19:00 |
| Chen 辰 | 07:00–09:00 | Xu 戌 | 19:00–21:00 |
| Si 巳 | 09:00–11:00 | Hai 亥 | 21:00–23:00 |
Why Zi hour is special
Zi straddles midnight: 23:00–24:00 is "late Zi", 00:00–01:00 is "early Zi". The dispute concerns the day pillar — should someone born at 23:30 use today's or tomorrow's day stem-branch?
- Day-change school: a new day begins at Zi; after 23:00 the next day's pillar applies
- Natural-day school: the day pillar follows the civil date; only the hour pillar takes Zi
Both positions have classical sources. The Guanming engine applies one deterministic rule, and in exact-time mode (entering e.g. 23:47) handles the day change automatically — after true-solar-time correction, so borderline cases resolve correctly.
If you only roughly know your birth time
- Remember the period ("around dawn"): use hour-mode and pick the closest double-hour
- No memory at all: compatibility readings offer an "hour unknown" option; the engine falls back to midday and flags it in the report
- Birth certificate with exact minutes: use exact-time mode plus your birth city for the most accurate pillar