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Chinese Double-Hour Calculator (时辰)

Converts a clock time to the traditional Chinese double-hour (时辰 shichen): its earthly branch (子 … 亥), animal and index, and, when a date is given, the hour's ganzhi (干支) by the 五鼠遁 (five-rats) rule from the day stem, with the option to count the late 子 hour (23:00–23:59) with the next day.

When to use

You need the 时辰 of a birth time or event (e.g. for a Bazi hour pillar), or the table of the twelve double-hours.

Do not use when: You need the full four pillars (use bazi-four-pillars), or you need to convert the clock time between time zones first (use time-zone-converter).

Formula

branch index = floor(((hour + 1) mod 24) / 2) (子 = 0 for 23:00–00:59); hour stem = ((day stem index mod 5) × 2 + branch index) mod 10 (五鼠遁: 甲己 days start 甲子, 乙庚 丙子, 丙辛 戊子, 丁壬 庚子, 戊癸 壬子)

Double-hours are fixed clock intervals of the local standard time; some schools use true solar time instead (add the longitude correction and equation of time before entering the time). The day stem uses the civil date, shifted to the next day for 23:00–23:59 when late_zi_next_day is true. Traditional calendar/cultural reference calculation; not a prediction, medical, legal or financial advice.

Inputs

ParameterTypeUnitRequiredDescription
timestringyes24-hour clock time HH:MM (local mean/standard time of the place; China Standard Time in China).
datedatenoOptional civil date (1900–2100) to obtain the hour ganzhi from the day stem.
late_zi_next_daybooleandefault truetrue (common Bazi convention): 23:00–23:59 uses the next day's stem; false: it keeps the current day's stem (早子/晚子 distinction).

Outputs

OutputTypeUnitDescription
hour_branchstringEarthly branch of the double-hour.
pinyinstringPinyin of the branch.
hour_namestringName and clock range, e.g. 未时 Wei hour, 13:00–14:59.
hour_indexinteger1 (子, 23:00–00:59) to 12 (亥, 21:00–22:59).
animalstringZodiac animal of the branch.
hour_ganzhistringStem and branch of the hour by the 五鼠遁 rule; only when date is given.
day_ganzhi_usedstringDay stem-branch whose stem generated the hour stem, with the date it belongs to; only when date is given.
is_late_zibooleantrue for 23:00–23:59 (晚子时).
tablelist12 rows: branch, pinyin, hours, animal (and ganzhi for the entered date when given).

Example

14:30 on 2026-09-24 (辛丑 day): {"time":"14:30","date":"2026-09-24","late_zi_next_day":true} → {"hour_branch":"未","pinyin":"Wei","hour_index":8,"animal":"Goat (羊)","hour_ganzhi":"乙未 (Yiwei)","is_late_zi":false}

23:30 on 2026-09-24 (late 子, next day 壬寅): {"time":"23:30","date":"2026-09-24","late_zi_next_day":true} → {"hour_branch":"子","hour_index":1,"hour_ganzhi":"庚子 (Gengzi)","is_late_zi":true}

GET https://tttkmbb.com/api/v1/calculate/chinese-hour?time=14%3A30&date=2026-09-24&late_zi_next_day=true

Machine access

Sources

FAQ

Why does 23:30 use the next day's stem?

The 子 hour spans midnight (23:00–00:59). Most Bazi schools treat 23:00–23:59 as the first hour of the following day (晚子时 belongs to the next day pillar); set late_zi_next_day=false to keep the current day's stem instead.

Should I use clock time or solar time?

Traditional almanacs assume local solar time. In China the clock (UTC+8) is up to about an hour ahead of solar time in the west of the country; convert first if your school requires true solar time.

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