Last revised: 2026-10-18
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About this page: this is the English edition of Foundations; the five language editions correspond one to one and in the same order.
The short pieces gathered here as Basics cover the few things one cannot get around when reading a calendar: which day a year begins on, when a day begins, where the sixty pairings of the stems and branches come from, and what each of the three roads in the sky governs. Each piece takes a single question; the fourteen stand on their own, and any one of them can be the first you read. The fourteen entries are on the English page; the five language editions correspond one to one and in the same order.
1 · Who these short pieces are for
These are written for readers who have no background in calendrics but want to know why things are the way they are. Technical terms are kept to a minimum, and where one cannot be avoided it is explained on the spot.
None of the fourteen is long. Each takes a single question, and any of them can be the first you read. Where a piece uses a phrase from an old text, the source is named in that piece; where numbers are involved, they are given in a form you can recompute yourself.
2 · Three threads
The fourteen run along three threads. The first is time itself: where the practice of announcing the hours came from, where a day begins, and where clock time parts company with the sun.
The second is the question of which day a year begins on: why three calendars run side by side, why the solar terms fall into two halves, whether the year turns at Lichun or at the first day of the first month, and what 正月 originally meant.
The third is the sky and its signs: what each of the three roads in the sky is measured against, how the twenty-eight mansions divide the sky, how direction was fixed before the magnetic needle came aboard, and where the stems, the branches and the sixty pairings come from.
3 · Related articles on this site, in reading order
- Why the Emperor Yao Sent Men to Watch the Stars: To Know When to Sow —— the appointment to observe the sky recorded in the Book of Documents. (no English edition yet; links to the Chinese text)
- How Is Time Produced? —— the sidereal day and the solar day differ by nearly four minutes a day.
- The Day Began at Eleven at Night: The Double-Hour and Its Measure —— 子, the first double-hour, is the point of the day furthest from the sun.
- Clock Time Is Not the Double-Hour of Your Birth —— clock time and true solar time are not the same thing.
- Three Calendars, Three Kinds of Time —— the three scales, and what each of them is set to.
- Nodes and Breaths: The Two Halves of the Twenty-Four Solar Terms —— why the twenty-four solar terms are divided into two halves. (no English edition yet; links to the Chinese text)
- Lichun Is Not a Day: The Solar Term Is an Instant —— a solar term begins at an instant fixed to the second.
- When Does the Year Turn: at Lichun, or at the First Day of the First Month? —— two conventions for the turning of the year have run side by side for over two thousand years. (no English edition yet; links to the Chinese text)
- “Zhengyue” Was Not Originally the First Month of the Year —— 正月 originally meant whichever month the year began in.
- Three Roads in the Sky: the Ecliptic, the Lunar Path and the Celestial Equator —— three roads, each answering a different question.
- The Ancients’ Sky: The Three Enclosures and the Twenty-Eight Mansions —— twenty-eight divisions, one scale laid over the sky.
- Without a Compass: How the Ancients Determined Direction —— how direction was fixed before the magnetic needle came aboard.
- Stems and Branches: From One Tree to Twenty-Two Characters —— 干支 was originally written 幹枝, “trunk and branches”.
- Ten Stems, Twelve Branches: Why Only Sixty Pairings Remain —— like pairs with like, and a hundred and twenty becomes sixty.
4 · How to read these fourteen
The fourteen are independent and need not be read in order; each piece ends with a short list of what to read next.
To follow the threads, start with How Is Time Produced? and Why the Emperor Yao Sent Men to Watch the Stars, which lay the groundwork for time itself; then take the pieces on the turning of the year; leave the two on the stems and branches for last, since that is another system of signs and does not share the same ruler as the first two groups.
All data on this page were collected and compiled by Chujia Kuang.