# The 12 Chinese Double-Hours (Shichen): How Your BaZi Hour Pillar Works

> Traditional Chinese timekeeping divides the day into twelve two-hour shichen, each named after an earthly branch. Here is the full table, the midnight zi-hour rule, and how the hour pillar's stem is derived.

## The short answer

Traditional Chinese timekeeping divides the day into **twelve double-hours (时辰, shichen)**, each two hours long and named after one of the twelve earthly branches. Your BaZi hour pillar's branch is simply the shichen you were born in; its stem is then derived from the day stem by a fixed rule. That is why a BaZi reading needs your birth *hour*, not just the date.

## The full shichen table

| Shichen | Branch | Clock time |
|---------|--------|-----------|
| 子 Zi | Rat | 23:00 – 00:59 |
| 丑 Chou | Ox | 01:00 – 02:59 |
| 寅 Yin | Tiger | 03:00 – 04:59 |
| 卯 Mao | Rabbit | 05:00 – 06:59 |
| 辰 Chen | Dragon | 07:00 – 08:59 |
| 巳 Si | Snake | 09:00 – 10:59 |
| 午 Wu | Horse | 11:00 – 12:59 |
| 未 Wei | Goat | 13:00 – 14:59 |
| 申 Shen | Monkey | 15:00 – 16:59 |
| 酉 You | Rooster | 17:00 – 18:59 |
| 戌 Xu | Dog | 19:00 – 20:59 |
| 亥 Hai | Pig | 21:00 – 22:59 |

Note the boundaries: a birth at 08:59 is a Dragon-hour birth; 09:00 is already Snake hour.

## The midnight problem: early vs late Zi hour

Zi hour straddles midnight (23:00–00:59), which raises a classical question: does a 23:30 birth belong to today's day pillar or tomorrow's?

- **Late-Zi school (晚子时)**: 23:00–23:59 keeps today's day pillar but uses the next day's Zi-hour stem.
- **Mainstream modern convention**: the day pillar changes at 23:00 — a 23:30 birth on the 5th is charted as the 6th's Zi hour.

Practitioners differ; what matters is that your calculator states which rule it applies. Our [free BaZi calculator](/chart) follows the **late-Zi convention**: a birth at 23:00–23:59 keeps that day's day pillar (verified against the engine directly — a 23:30 birth on January 5, 2026 charts as the 己卯 day, not the next day's 庚辰). Boundary births are worth reading under both rules.

## How the hour stem is derived (the "Five Rats" rule)

The hour pillar's heavenly stem is not independent — it follows from the **day stem** via the traditional 五鼠遁 ("Five Rats escaping") formula. Days whose stem is 甲 or 己 start their Zi hour with 甲; 乙/庚 days start with 丙; 丙/辛 days with 戊; 丁/壬 days with 庚; 戊/癸 days with 壬. The remaining eleven hours then follow the stem cycle in order.

So a 甲-day birth in Mao hour (05:00–06:59) has the hour pillar 丁卯 — counted four steps from 甲子.

## Why the hour matters so much

The hour pillar governs the chart's "time palace" — classically read for later life, children, and the day-to-day expression of the day master. Two people born on the same day but in different shichen can have meaningfully different charts: a different hour branch changes the five-element balance, and a different hour stem changes which "ten god" sits beside the day master.

If you don't know your birth hour, a chart can still be read from three pillars — but any statement that depends on the hour pillar should be treated as undetermined rather than guessed.