The Chinese Calendar: Solar Terms, Li Chun and When the Year Begins

Almost every confusion in Chinese metaphysics that is not about compasses turns out to be about the calendar. The traditional calendar is not lunar, and it is not solar: it runs twelve lunar months and then keeps them in step with the seasons by other means, so it carries two different "new years" and two different ways of telling the time of year. Feng shui and BaZi use the solar half of it, and the moment when that half changes is not the date most people celebrate.

This article sets out the mechanism: what the calendar is made of, when the year turns, and where the seams are. It is deliberately free of the current year's dates — the Feng Shui tools and the calculators give those, and they change every year while the mechanism does not.

1. A calendar that is both lunar and solar

The months of the Chinese calendar are lunar. A month begins on the day of the new moon and runs to the day before the next one, so a month is about twenty-nine or thirty days long and drifts against the seasons: twelve of them fall short of the solar year by a margin that accumulates year on year.

If the calendar were purely lunar, the first month would wander through the seasons within a generation, and a system whose readings depend on the time of year would be impossible. So the calendar corrects itself by repeating a month when the drift has built up, which is why it is called lunisolar: lunar months, fitted to the solar year.

Alongside the months runs a second structure that ignores the moon entirely. The year is divided into 24 solar terms (節氣, jieqi), each marking a specific point in the sun's annual progress, and each falling on a date that hardly moves from year to year. These terms are the skeleton of the whole system. Feng shui reads the year by them, and so does the 60 Jiazi cycle that names the years.

2. Two new years

Because the calendar has a lunar face and a solar face, it has two beginnings, and they can fall weeks apart.

The lunar New Year is the first day of the first lunar month — the festival known as the Spring Festival, or simply Chinese New Year. Being a lunar date, it moves through late January and February from year to year, sometimes landing before the solar beginning of the year and sometimes after it.

Li Chun (立春), "the beginning of spring", is the solar new year. It is one of the 24 solar terms, and it falls around 4 February — closer to a fixed date than anything lunar can be.

The distinction is not academic. Everything that is measured in years in this tradition turns at Li Chun:

• the year pillar in a BaZi chart, and the year's animal with it;
• the Kua number of anyone born in the contested weeks, since its arithmetic starts from the birth year and the birth year is the solar one;
• the annual chart — the Flying Stars of the year — and the annual afflictions that move with it.

The trap is threefold, and it catches experienced people. The year does not change on 1 January, it does not change at the lunar New Year, and it does not change with the four Western seasons. It changes at Li Chun, which falls around 4 February. A birth on 20 January belongs to the previous year by every rule in this tradition, however the family celebrated it.

3. The 24 solar terms

The 24 terms divide the solar year into twenty-four equal steps of about fifteen days each. They come in two kinds, alternating around the year, and the two kinds do different work.

3.1 The twelve jie that open the months

Twelve of the terms are called jie (節). Each one opens a solar month, and each solar month is named by an Earthly Branch. The sequence begins at Li Chun, which opens the month of the Tiger (寅) — the first month of the solar year — and runs through the twelve terms listed in the table below. A month pillar in BaZi changes when its jie arrives, not when a lunar month begins, which is why the month pillar and the lunar month number can disagree in the same week.

3.2 The twelve qi in the middle

The other twelve terms are called qi (氣). They fall roughly in the middle of each solar month and mark the character of the season rather than its boundary: the spring equinox, the summer solstice, the winter solstice, the great heat, the descent of frost. They are the terms people know best as calendar dates, and in the older reckoning they are what a month must contain — a point that matters for the leap month in section 5.

4. The terms and their usual dates

The dates below are the ones the terms normally fall on. They move by about a day from year to year according to the leap-year pattern, so any of them may land on the neighbouring date; the table is a guide to the calendar's shape, not a table of fixed dates.

#	Solar term	Characters	Usual date	Kind	Opens
1	Li Chun	立春	4 February	Jie	Tiger month
2	Yu Shui	雨水	19 February	Qi	—
3	Jing Zhe	惊蛰	5–6 March	Jie	Rabbit month
4	Chun Fen	春分	20–21 March	Qi	—
5	Qing Ming	清明	4–5 April	Jie	Dragon month
6	Gu Yu	谷雨	20 April	Qi	—
7	Li Xia	立夏	5–6 May	Jie	Snake month
8	Xiao Man	小满	21 May	Qi	—
9	Mang Zhong	芒种	5–6 June	Jie	Horse month
10	Xia Zhi	夏至	21 June	Qi	—
11	Xiao Shu	小暑	7 July	Jie	Goat month
12	Da Shu	大暑	22–23 July	Qi	—
13	Li Qiu	立秋	7–8 August	Jie	Monkey month
14	Chu Shu	处暑	23 August	Qi	—
15	Bai Lu	白露	7–8 September	Jie	Rooster month
16	Qiu Fen	秋分	22–23 September	Qi	—
17	Han Lu	寒露	8 October	Jie	Dog month
18	Shuang Jiang	霜降	23 October	Qi	—
19	Li Dong	立冬	7–8 November	Jie	Pig month
20	Xiao Xue	小雪	22 November	Qi	—
21	Da Xue	大雪	7 December	Jie	Rat month
22	Dong Zhi	冬至	21–22 December	Qi	—
23	Xiao Han	小寒	5–6 January	Jie	Ox month
24	Da Han	大寒	20 January	Qi	—

Read down the Opens column and the whole of BaZi month reckoning is visible: twelve solar months, each opened by its jie, beginning with the Tiger. The same twelve months are what the twenty-four mountains of the compass divide more finely, as the reference tables show.

5. The leap month

A lunar month is roughly twenty-nine or thirty days, so twelve of them fall short of the solar year by a margin that grows with every year that passes. Left alone, the calendar would slip out of the seasons. The correction is a repeated month: a leap month is inserted, and the calendar then carries thirteen months in that year.

The leap month is not added arbitrarily. On the older reckoning, a month that contains no qi is not a proper month and cannot carry a month number; it is repeated as the leap month of the month that precedes it, and the numbering continues around it. The correction comes round roughly once every three years, which is enough to keep the lunar and solar faces of the calendar together over long stretches.

The practical consequence for a chart is mild but real: the lunar month numbering shifts in a leap year, and anyone who works from lunar dates rather than from solar terms will be a month out at exactly the points where it matters.

6. When the day begins

The traditional Chinese day begins at 23:00, not at midnight, because the twelve double-hours are counted from the Zi (子) hour, and the Zi hour straddles midnight: it runs from 23:00 to 01:00. Under that reckoning a birth at half past eleven at night belongs not only to the next day's early hours but to the next day's pillar.

Modern software does not always follow the classical convention. Some calculators count the day from midnight, on the plain reading of a clock; others start the new day at 23:00 in the traditional manner. Both customs are in circulation, and the difference only shows up for births in that one-hour window between 23:00 and midnight — but for those births it changes the day pillar, and with it the Day Master of the whole chart.

If someone you know was born between 23:00 and midnight and their chart has never quite fitted, this is the first thing to check. It is not an error in the chart; it is a choice of convention, and the two conventions give two different days.

7. Why this matters in feng shui

The calendar is not background knowledge in this tradition; it is the input.

The annual layer of feng shui moves at Li Chun. The year's Flying Stars chart is drawn for the solar year, and the annual afflictions — Tai Sui, Sui Po and San Sha — take their positions for the same span. A remedy applied in January against a sector that is about to change hands is a month of work devoted to the wrong corner.

The personal layer depends on the same boundary. The Kua number is calculated from the solar year of birth, so for anyone born in the first weeks of a year the answer hinges on Li Chun rather than on a birth certificate's date.

And the chart itself is made of pillars. BaZi is entirely a calendar construction — four pairs of Stem and Branch read from the solar year, the solar month, the continuous day count and the double-hour — so a BaZi reading is only as good as the calendar it was taken from. Where time sits among the other inputs of the tradition — form, compass and person — is set out in Feng Shui.

8. Frequently Asked Questions

Is the Chinese calendar lunar or solar?

It is both, which is why it is called lunisolar. The months are lunar — they begin on the new moon — while the year is kept in step with the seasons by the 24 solar terms and by inserting a leap month when the drift requires it. Feng shui and BaZi work from the solar terms rather than from the months; the BaZi calculator applies them for you.

Does the feng shui year change at Chinese New Year?

No. The lunar New Year, or Spring Festival, is a lunar date and moves through late January and February. The year that feng shui and BaZi use changes at Li Chun (立春), around 4 February, so the two can fall weeks apart and in either order. Charts, the Kua number and the annual afflictions all turn at Li Chun.

Why do the solar terms move by a day from year to year?

Because the solar year is not a whole number of days, and the calendar counts whole days. The terms fall at fixed points in the sun's progress, but those points land on a slightly different clock date each year, which is the same reason the equinox moves in the Western calendar. The table in this article gives the usual dates, not fixed ones.

Why is there sometimes a leap month?

Because twelve lunar months are shorter than the solar year, and the shortfall accumulates. When it has built up, a month is repeated so that the calendar stays in step with the seasons. On the classical rule, a month containing no qi cannot hold a month number and becomes the leap month of the month before it. The correction comes round roughly once every three years.

Does the day really start at 23:00?

In the traditional count, yes: the twelve double-hours begin with the Zi hour, which runs from 23:00 to 01:00, so the new day begins at eleven in the evening. Some modern software instead starts the day at midnight. Both conventions are in use, and they give different day pillars for births in that hour.