The 12 Double Hours and Modern Clock Time
Map the twelve Earthly Branch hours to modern two-hour intervals and apply the mapping only after the chart’s time basis is resolved.
Overview
Traditional Chinese timekeeping divides a day into twelve branch-labeled periods, commonly rendered as double hours because each spans about two modern hours. In the standard modern mapping, Zi covers 23:00–00:59, Chou 01:00–02:59, and the sequence continues every two hours until Hai at 21:00–22:59. This table classifies the final local clock used by the Bazi method; it does not decide whether that clock is civil, mean solar or apparent solar time, and it does not by itself settle whether the Day Pillar changes at 23:00 or midnight.
At a glance
- Number of periods
- 12 branch-labeled intervals per day
- Typical duration
- Two modern clock hours each
- First interval
- Zi: 23:00–00:59
- Midday interval
- Wu: 11:00–12:59
- Final interval
- Hai: 21:00–22:59
- Separate choice
- Day-Pillar rollover convention
The branch sequence advances in two-hour intervals
The standard sequence is Zi 23:00–00:59, Chou 01:00–02:59, Yin 03:00–04:59, Mao 05:00–06:59, Chen 07:00–08:59 and Si 09:00–10:59.
It continues with Wu 11:00–12:59, Wei 13:00–14:59, Shen 15:00–16:59, You 17:00–18:59, Xu 19:00–20:59 and Hai 21:00–22:59. Exact boundary handling uses the calculator’s supported precision.
- Keep the canonical Earthly Branch order.
- Classify 24-hour values without rounding.
Map the final declared clock, not every intermediate clock
Historical civil time is resolved first. If the selected method uses local mean or apparent solar time, perform those corrections before looking up the hour branch.
Applying the table once to civil time and again to solar time without labeling them creates competing charts. Save the basis used for the canonical result.
- State civil, mean-solar or apparent-solar basis.
- Apply the branch table only after conversion.
Zi hour spans midnight, but day rollover is a separate rule
The Zi branch begins at 23:00 in the common mapping and continues after civil midnight. Some Bazi schools change the Day Pillar at 23:00, while others retain a midnight boundary or distinguish early and late Zi.
The hour table alone cannot resolve that doctrinal choice. Store the day-boundary convention and recompute the Hour Stem from the effective Day Stem.
- Do not equate Zi start automatically with day change.
- Expose the selected rollover rule.
A double hour is a classification interval, not a Western zodiac hour
The branch label becomes the Hour Branch and combines with a stem derived from the Day Stem. It is not one-twelfth of variable daylight, nor a separate Western planetary-hour system.
The label does not carry a complete personality judgment by itself. Interpretation requires the full Four Pillars and the same evidence hierarchy used elsewhere.
- Keep the calendrical systems distinct.
- Do not read one hour branch in isolation.
Sources and editorial basis
- Hong Kong Observatory: Heavenly Stems and Earthly Branches香港天文台說明干支循環與時干對應表，支持十二地支時辰的標準順序與由日干推時干的結構An official modern reference for the canonical stem and branch orders, the sexagenary cycle, and calendrical use.
- OpenFate Editorial Methodology產品在歷史時區與所選太陽時轉換完成後才配置時支，並把子時區間與 23:00 或 00:00 換日約定分開保存OpenFate separates deterministic chart calculation, traditional interpretation, and modern editorial explanation.