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Double-hour chart coordinate · 時柱

The clock opens the hour pillar

The clock selects the hour branch, but it does not select the complete pillar. The 五鼠遁 Five Rats rule uses the day stem to supply a matching hour stem, so the same animal hour can carry five different pairs.

Four inscribed chart tablets in a Chinese observatory pavilion at the turn from night to dawn
時柱The hour tablet is the smallest time scale in the chart and the only pillar that cannot be recovered when a birth time is absent.

Stem above · branch below

What a known birth time contributes

A local civil time fixes one of twelve branch periods. The day stem then determines which of five parity-valid Heavenly Stems accompanies that branch.

  1. 01Visible stemDerived hour stem

    The Five Rats rule begins from the Day Master and advances with the branch.

  2. 02Visible branchOne two-hour period

    Rat begins at 23:00; each later branch begins two civil hours after it.

  3. 03Time scale120 civil minutes

    A minute matters at the branch edge and at the late-Rat day boundary.

  4. 04Chart roleFourth visible pair

    Without a time, two of the eight visible characters remain unknown.

Where this coordinate changes

Twelve branch periods divide the civil-clock day

The calculator uses the local civil time entered. It does not silently infer a place, daylight-saving history, longitude correction or apparent-solar-time school.

  1. 01 · Opening

    Rat runs 23:00–00:59

    子 is the only branch period that crosses the Gregorian date boundary.

  2. 02 · Sequence

    Each branch then holds two hours

    Ox begins at 01:00, Tiger at 03:00, and the fixed order continues until Pig ends at 22:59.

  3. 03 · Missing input

    No birth time means no hour pillar

    Assuming noon or another convenient time would invent both a branch and a stem, so the result remains absent.

The rule, not a personality shortcut

The Five Rats rule supplies the hour stem

The day stem group chooses the Heavenly Stem placed over the opening Rat hour. From there, the stem advances once for each next branch period.

Day Master group → Rat-hour stem → advance once per two-hour branch

  1. 甲 / 己 days

    甲子 · Jia Rat

    Jia and Ji Day Masters open Rat hour with the Jia Wood stem.

  2. 乙 / 庚 days

    丙子 · Bing Rat

    Yi and Geng Day Masters open with the Bing Fire stem.

  3. 丙 / 辛 days

    戊子 · Wu Rat

    Bing and Xin Day Masters open with the Wu Earth stem.

  4. 丁 / 壬 days

    庚子 · Geng Rat

    Ding and Ren Day Masters open with the Geng Metal stem.

  5. 戊 / 癸 days

    壬子 · Ren Rat

    Wu and Gui Day Masters open with the Ren Water stem.

Keep the coordinate precise

Common hour pillar confusions

These distinctions prevent one useful label from being stretched into a claim the chart does not make.

01
Is my zodiac hour animal the complete hour pillar?
No. The animal names only the branch. A complete pillar also needs the Heavenly Stem derived from the Day Master.
02
Can the hour pillar be calculated without a birth time?
No. A date alone does not identify the two-hour branch, so neither character can be responsibly supplied.
03
Does this site convert civil time to apparent solar time?
No. It uses the local civil time entered and states that convention. Solar-time correction requires a declared method and location data.