The 12 Chinese hours and true solar time
Chinese astrology splits the day into 12 double-hours. Your Chinese hour sets the Life Palace, so the clock time of birth must first be converted to true solar time at the place of birth.
The 12 Chinese hours
| Chinese hour | Starts | Ends |
|---|---|---|
| 子（Zi） | 23:00 | 01:00 |
| 丑（Chou） | 01:00 | 03:00 |
| 寅（Yin） | 03:00 | 05:00 |
| 卯（Mao） | 05:00 | 07:00 |
| 辰（Chen） | 07:00 | 09:00 |
| 巳（Si） | 09:00 | 11:00 |
| 午（Wu） | 11:00 | 13:00 |
| 未（Wei） | 13:00 | 15:00 |
| 申（Shen） | 15:00 | 17:00 |
| 酉（You） | 17:00 | 19:00 |
| 戌（Xu） | 19:00 | 21:00 |
| 亥（Hai） | 21:00 | 23:00 |
Times in the table are true solar time, not clock time.
How true solar time is worked out
- Longitude: every degree away from your time zone's meridian is 4 minutes. London sits almost on 0°, so the correction is tiny; Madrid, at 3.7° west on UTC+1, runs about 75 minutes behind the clock in winter.
- Daylight saving: if it was in force on your birth date, subtract one more hour.
- Equation of time: through the year the sun runs between 14 minutes slow and 16 minutes fast.
If you were born within 15 minutes of a boundary between two Chinese hours, the correction can change your chart. Our calculator does all three steps and warns you when you are close.
Questions
What time is the Zi hour?
23:00 to 01:00 true solar time.
Why not use clock time?
Clock time is shared by a whole time zone; the sun is not. The gap can exceed an hour.