Case 17 of 26
Zi Hour and midnight
Before corrected midnight: sect 2 keeps the current Day Pillar
A 23:45 true-solar result is already in Zi Hour but still on the same Bazi day under sect 2.
Boundary question
Does the Day Pillar remain stable from 23:00 to 00:00 after correction?
Yes. The Day Pillar is still Wu-Wu (ζε), while the Hour Pillar is Jia-Zi (η²ε).
Synthetic input
Recorded facts
- Date
- 2026-06-13
- Recorded time
- 23:45
- Location
- 120Β°E reference meridian
- Time zone
- Asia/Shanghai
- Longitude
- 120.0000Β°
- Gender input
- Male
Pinned expected facts
Verified output
Year
δΈε
Month
η²ε
Day
ζε
Hour
η²ε
- Day Master
- ζ
- True solar time
- 2026-06-13 23:45
- Total correction
- 0.29 minutes
- Historical offset
- UTC+08:00 Β· DST 0 min
- Luck direction
- ι‘Ίζ
- Reference Jie
- ε°ζ Β· 2026-07-07 09:56:57
- Luck start
- 2034-04-03 23:05:17
Reading the boundary
What this case means for your own chart
At 23:45 true solar time the record is well inside Zi Hour but still on the same Bazi day. This case and the next form a second controlled pair, testing the other half of the boundary: midnight itself rather than the 23:00 mark.
Reading the four cases in this category in order gives a complete picture of one night. At 22:45 the hour is Gui-Hai and the day is unchanged. At 23:15 and 23:45 the hour is Jia-Zi and the day is still unchanged. Only after midnight does the day pillar move. There is no point in the sequence where the hour and the day change at the same instant.
That is what a reader should take away. The two boundaries are thirty to sixty minutes apart depending on the convention, and a birth record that lands between them is the case where the choice of school changes the chart most visibly.
The sequence also shows why a single example cannot illustrate this rule. Any one of the four records, read alone, looks unremarkable. It is the progression across the hour and a half that makes the structure visible, which is the reason this site publishes four cases rather than one and labels them as a set.
Check your own record
- If you were born in the last hour before midnight, confirm your calculator's day-boundary convention before reading anything from the day pillar.
- Plot your corrected birth time against both 23:00 and 00:00 rather than against a single remembered rule.
- Expect the hour pillar to be the more stable of the two in this window, since all conventions agree Zi Hour has begun.
Which convention is in play
- Calculation fact
- The pinned engine returns a Jia-Zi hour pillar with the Wu-Wu day pillar unchanged at 23:45 true solar time, the same values as the 23:15 case.
- Convention
- That the day pillar holds from 23:00 to 00:00 is specific to the sect 2 convention. Under the alternative, this record would already belong to the next day.
- Our explanation
- Our advice to expect the hour pillar to be the more stable value in this window follows from the stated convention and applies only while that convention holds.
Conventions and limits
What this case does β and does not β prove
It verifies
Deterministic reproduction of this input under the named engine version and conventions. A pinned-field mismatch stops the production build.
It does not claim
Universal agreement across Bazi schools, interpretation of a real person, or certainty where the historical record is incomplete.
tyme4ts 1.5.2 Β· sect 2 day boundary Β· BaziCalculator.ai NOAA/IANA true-solar adapter
calculation-benchmarks-v1 Β· reviewed 2026-09-05