年 · 月 · 日 · 時 · four nested clocks
Four clocks in one chart
A chart does not begin with four personality labels. It locates one moment on four advancing cycles: year, solar month, day and double hour. Each supplies a stem and a branch, and each changes at a boundary of its own.
One date · four coordinates
The four clocks do different work
The same birth moment is counted in units of years, seasonal months, days and two-hour periods. A branch names the position on each cycle; a stem completes each pillar.
- 01Year pillar
A stem–branch coordinate whose Four Pillars boundary is Li Chun; the popular outer animal here turns at Chinese New Year.
Open the guide → - 02Month pillar
One of twelve branch months opened by the alternating jie solar terms, not by Gregorian month starts.
Open the guide → - 03Day pillar
One position in the continuously advancing sixty-day count; its stem is the Day Master.
Open the guide → - 04Hour pillar
A two-hour branch paired with a stem derived from the day stem. It cannot be recovered without a birth time.
Open the guide →
Edges matter
A boundary is part of the answer
Two results can differ without either arithmetic being wrong when they name different turning points. The convention must stay visible beside the result.
- 01Chinese New Year
Turns the familiar outer-animal year used by the zodiac-year calculator.
Date guide → - 02Li Chun
Turns the Four Pillars year and opens the Tiger branch month.
Compare boundaries → - 03Twelve jie terms
Open the twelve branch months at astronomical moments that drift by year.
Term atlas → - 0423:00 and midnight
The Rat hour wraps midnight; published day-pillar schools can differ during its first civil hour.
Rat hour →
Clock and place
A recorded time still needs a method
Modern birth records use civil time. Historical practice predates standard time zones, and some contemporary schools adjust for longitude or apparent solar time. This site deliberately uses the local civil time entered and does not silently transform it.
What the calculator can know
A valid local date and time locate the civil-clock double hour and let the calendar library derive all four pillars. On a solar-term day, the stated time also decides which month contains the birth.
What it cannot infer
A place name, historical time-zone rule, daylight-saving correction or chosen solar-time school cannot be reconstructed from a bare clock reading. Those require explicit location and method inputs.